Multi-user mimo via active scattering platforms

ABSTRACT

A communication system includes a transmitter, one or more active scattering platforms, and one or more remote receivers. The transmitter includes a beam forming network for transforming M signals into a set of shaped beams which are radiated toward the active scattering platforms by transmitter antenna elements. The active scattering platforms receive and re-radiate one or more of the radiated shaped beams toward the receivers. The beam forming network optimizes composite transfer functions under performance constraints. Each composite transfer function is a linear combination of transfer functions. Each transfer function characterizes propagation paths from one transmitter antenna element to one receiving antenna element. Each receiving antenna element is identified by a user element identification index in the transfer functions. Each receiver is identified by a user identification index. The performance constraints are specified for locations identified by the user identification indices or the user element identification indices.

RELATED APPLICATIONS

This application is a continuation of application Ser. No. 14/193,540filed on Feb. 28, 2014, which claims priority to U.S. provisionalapplication No. 61/903,909, filed on Nov. 13, 2013, which isincorporated herein by reference in its entirety. This application isalso related to the following applications, which are incorporatedherein by reference in their entireties:

U.S. patent application Ser. No. 13/623,882, filed on Sep. 21, 2012,entitled “Concurrent Airborne Communication Methods and Systems”, nowU.S. Pat. No. 8,767,615, issued on Jul. 1, 2014;

U.S. patent application Ser. No. 13/778,171, filed Feb. 27, 2013,entitled “Multi-Channel Communication Optimization Methods and Systems”,now U.S. Pat. No. 9,596,024, issued on Mar. 14, 2017; and

U.S. patent application Ser. No. 14/182,665, filed Feb. 18, 2014,entitled “Multi-User MIMO via Frequency Re-Use in Smart Antennas”.

TECHNICAL FIELD

MEMO communications channels provide an interesting solution tomultipath challenges by requiring multiple signal paths. In effect, MIMOsystems use a combination of multiple antenna elements and multiplesignal paths to gain knowledge of a communications channel. By using thespatial dimension of a communications link, MIMO systems can achievesignificantly higher data rates than traditional single-input,single-output (SISO) channels. In a 2×2 MIMO system, signals propagatealong multiple paths from the transmitter to the receiver antennas.Using this channel knowledge, a receiver can recover independent streamsfrom each of the transmitter's antennas. A 2×2 MIMO system produces twospatial streams to effectively double the maximum data rate of whatmight be achieved in a traditional 1×1 SISO communications channel.

The present invention relates to multiple-usermultiple-input-multiple-output (MU MIMO) communications systems, as wellas communications via fixed platforms such as base stations, mobile andrelocatable ground platforms, air platforms such as UAVs, andsatellites. It is also related to wavefront multiplexing/de-multiplexing(WF muxing/demuxing) technologies. The present invention relates tomultiple-user multiple-input-multiple-output (MU MIMO) communicationssystems through multipath propagation scattering from multipletransponding platforms; including unmanned air vehicles (UAVs),geo-stationary earth orbit (GEO) satellites, and non-geostationary earthorbit (NGEO) satellites. Transponding RF signals on a platform comprisesof functions of receiving RF signals, low-noise-amplifying the receivedRG signals, filtering the amplified received signals, frequencytranslating the filtered signals, power-amplifying the frequencytranslated signals, and re-radiating the amplified signals. Amultiple-user multiple-input-multiple-output (MU MIMO) communicationssystem for a point-to-multipoint (p-to-mp) via a composited transferfunction technique for efficient frequency reused is described. One ofthe key features of the MIMO systems is a multipath dominatedcommunications channel comprising of multiple active scatteringplatforms. As a result, a multipath propagation channel from a source tomultiple destinations will not only be measurable but also controllablevia these active scattering platforms to more efficiently providefrequency reuse among multiple users via discriminative propagationfeatures to various destinations.

The invention is also related to wavefront multiplexing/de-multiplexing(WF muxing/demuxing) technologies. The objectives for the invention isto provide means for (1) multiple users to re-use allocated spectrumconcurrently in MIMO communications configurations, and (2) enablingthese users to share allocated resources dynamically and efficiently.Conventional MIMOs take advantage of scattering in a multi-pathdominated communication channel which is typically characterized by many“transfer functions”. A transfer function, hij, is for typicalmeasurements of propagation delays and attenuation from an ith sourceelement in transmit to a jth destination element in receiving throughthe multipath dominated communications channel.

SUMMARY OF THE INVENTION

This disclosure describes exemplary embodiments on improving theoperation and use of MIMO communication methods and systems for multipleusers (MU) to re-use same spectrum such as through channel stateinformation (CSI) to form user-selection and/or rejection processing intransmission side. Embodiments pertain to wireless communicationsthrough a multipath dominant channel; where the multipaths are throughman-made active scattering platforms. These platforms are in parallelpaths providing amplifications, delays and directional adjustments froma signals source to a destination. When the sources and destinations areon ground in many embodiments, airborne platforms serve as bent-pipetransponders, which perform receiving, low-noise-amplifying, filtering,frequency translating, power-amplifying, and re-radiating functions forserving signals through the platforms.

This disclosure on MU-MIMO is summarized as followed;

-   -   MIMO Communications channels from a transmitting source to        multiple receiving destinations are through active scattering        from many transponding platforms    -   Frequency reuse is accomplished by directional diversity in        transmitters via formulations of point-to-multipoint (p-to-mp)        composited transfer functions and optimizations on the        formulated functions under multiple specified performance        constraints for user identifications and discriminations.    -   Optimizations are through beam shaping techniques under        performance constraints associated with locations indexed by        user identifications or indexed by user element identifications.    -   A composited transfer function is optimized to represent an        optimally shaped beam, featuring a point-to-multipoint (p-to-mp)        characteristics including integrated effects of transponding        platforms; with favorable connectivity for one specified user        and discrimination against others    -   a composited transfer function        -   i. used for specified performance constraints for a shaped            transmitting beam which features p-to-mp with connectivity            for one user and discrimination against others        -   ii. a radiation pattern of shaped beam is a linear            combination from radiation patterns of multiple transmitting            elements        -   iii. performance constraints for optimization via            -   1. Orthogonal beam (OB) criteria            -   2. Quiet zone criteria, and            -   3. others.    -   multiple concurrent transmit beams are optimized under        performance constraints by a set of many composited transfer        functions    -   different signal streams for various destinations are sent via        multiple shaped transmitting beams,    -   WF muxing/demuxing are incorporated as effective means for        dynamic allocations on communications resources (bandwidth and        RF power) among multiple users.    -   examples of many different configurations are presented.

In some embodiments, MIMO configurations feature a point-to-point(p-to-p) architecture with a source at a communication hub viaradiations from multiple base-stations (BS) to a destination in a commoncoverage of these BS's which are on transponding platforms. The MIMOconfigurations may also feature a point-to-multipoint (p-to-mp)architecture with a source at a communication hub via radiations frommultiple base-stations (BS) to multiple destinations in a commoncoverage of these transponding platforms.

In the MIMO systems of present invention, the serving signals fortransmission to user equipment (UE) via multiple paths will utilizecomposited transfer functions selected and characterized based onchannel state information (CSI); which comprises of responses fromprobing signal sequences for a propagation channel dominated bymultipaths in accordance with a dynamic user distribution. Eachpropagating path features a set of unique transponding functions. Thecomposited transfer functions are constructed or shaped to be “userdependent” with enhanced responses to a selected user and suppressedones for other users. When operating in coordinated modes, morecooperating UEs are configured to suppress interference to other UEusing the same frequency resources. Optimization methods for thecomposited transfer functions based on selected criteria are presentedin latter sections.

Some embodiments relate to coordinated point-to-multipoint (p-to-mp)communications in spoke- and hub configurations. The criteria forshaping the composited transfer functions for a transmitter in acommunications hub may include those in many beam-shaping techniques;such as orthogonal beams (OB), quiet-zones, and others. Some embodimentsrelate to wavefront multiplexing (WF muxing)/demultiplexing (demuxing)as means for coordinated or organized concurrent propagations throughmultipath dominated channels. As a result, methods for calibrations andequalizations among multiple path propagations become possible. Some arethrough forward paths only. Consequently, implementations of techniqueson coherent power combining in receivers for enhance signal-to-noiseratios (SNR) are simple and cost effective.

BACKGROUND

Wireless communication using multiple-input multiple-output (MIMO)systems enables increased spectral efficiency for a given total transmitpower. Increased capacity is achieved by introducing additional spatialchannels in multipath dominant propagation environment, which areexploited by various techniques such as spatial multiplexing, space-time(Block) coding and others as a part of pre-processing to maximizeisolations among these parallel channels. Many MIMO systems featureenhanced spectral efficiency for single users. A single use MIMOfeatures a single multi-antenna transmitter communicating with a singlemulti-antenna receiver. Given a MIMO channel, duplex method and atransmission bandwidth, a system can be categorized according to (1)flat or frequency selective fading, and/or (2) with full, limited, orwithout transmitter channel state information (CSI).

In contrast, multi-user MIMO (MU-MIMO) is a set of advanced MIMOtechnologies where the available antenna elements are spread over amultitude of independent access points and independent radioterminals—each terminal with one or multiple elements. To enhancecommunication capabilities of all terminals, MU-MIMO applies an extendedversion of space-division multiple access (SDMA) to allow multipletransmitters to send separate signals and multiple receivers to receiveseparate signals simultaneously in the same frequency or time slots, orwith same codes in the same frequency or time slots. There have beenmany MIMO-OFDM systems for multiple users' applications. Different userswill use various sets of frequency slot distribution patterns over thesame bandwidth over which orthogonal frequency components are radiated.

Our techniques exploit three aspects of propagation channels formultiple user MIMO systems; (1) the multiple parallel paths are throughmultiple active bent-pipe transponding platforms; (2) shaping MIMOchannel transfer functions based on available channel state information(CSI) at transmission side including effects of propagating throughmultiple transponding platforms, and (3) applying WF multiplexing toefficiently sharing power and bandwidth provide by these transpondingplatforms among multiple users.

Transponding platforms include ground based basestations (BS), airborneplatforms, and satellites. The airborne platforms may comprise ofunmanned air vehicles (UAVs) equipped with transponders, which may be aslarge as in wing spans >100 ft carrying >10 medium or low powertransponders operated above 10 Km in stratosphere, or as small as lessthan 6 inches carrying only one set of low power transponding devicesusually operated at a height <1 km. Medium or low power transponders arereferred to those with ˜10 Watt or ˜1 Watt radiated RF power,respectively. Transponding satellites may be configured as powerful as ahigh power communications satellite in geo-stationary earth orbit (GEO)with slightly less than 20 KW total DC power and >5000 Kg gross weightcarrying >100 transponders with a height of ˜10 m with unfolded antennasand a width of ˜50 m measured with deployed solar panels. Some oftransponding satellites may also be configured as small as a microsatcarrying a low to medium power transponder in low earth orbits (LEO)with ˜10 W in total DC power, ˜1 Kg in gross weight, and a 10 cm cube involume.

Present invention features additional pre-processing at transmissionside on available channel state information (CSI) which is formulatedvia channel transfer functions/matrixes, simply composited transferfunctions (CTFs), or composited transfer matrixes. The preprocessors arebuilt via linear combinations of multiple transmitting antennas by beamforming networks, “shaping” the MIMO transfer functions. As a result,the inputs of the preprocessors become accessible to user-selectablecomposited transfer functions (CTFs), which are optimized via shapingand optimization algorithms; similar to many in smart beam shapingtechniques. However, discrimination parameters for a composited transferfunctions are not “constrained” in directions as those specified inconventional shaped beams. The constraints in the composited transferfunctions are identified (ID) as “user indexed” or specified as “user IDindexed”. These user indexed performance constraints effectively enableoptimizations for composited transfer functions so that frequency re-usevia “directional diversity” become possible.

To make clear of meaning of a few technical terms related to multiple“active scattering platforms” in this application, we summarize a fewbelow.

-   -   i. Active scattering platforms feature communications        electronics which receive RF signals originated from a remote        transmitter from a given direction through a receiving antenna.        The received signals are amplified, filtered, “further        processed”, and then power amplified before re-radiated toward        various directions via a transmitting antenna. The pointing        directions and coverage of the receiving and the transmitting        antennas may not be the same. As a result, the incoming RF        signals to these active scattering platforms are much weaker        than the intensity levels of the re-radiated RF signals in        various directions. The re-radiated RF signals may be “biased”        to a preselected field of view (FOV).    -   ii. The FOV for the re-radiated RF signals may be remotely        configurable    -   iii. The “further processed” may include frequency translations.        In those cases the communications electronics on the active        scattering platforms are transponders.    -   iv. When the transponding platforms are mobile airborne or space        borne without de-modulations and re-modulations, their        communications electronic payloads are non-regenerative        transponders.    -   v. When users, including both transmitters and receivers        remotely connected to the transponding platforms, are on ground        or near ground, the non-regenerative electronic payloads are        “bent-pipe” transponders.    -   vi. The transponding platforms may be dynamically distributed,        ground base or near ground base, while remote users (either        transmitting or receiving) are airborne or space borne. This        feature shall be applicable of setting up a set of ground base        crosslinks among low-earth-orbit (LEO) satellites via MIMO        techniques.    -   vii. A p-to-p MIMO channel for enhanced channel capacity via        frequency reused is built on the randomness of a dynamic        distribution of the multiple platforms which feature a common        coverage.    -   viii. For a p-to-mp scenario, each transponding platform will        carry an aggregation of many sets of partial information to        various receivers.    -   ix. A p-to-mp MIMO channel for multi-users via frequency        re-usage is built on a randomness of a different dynamic        distribution of the multiple platforms which feature concurrent        but discriminative coverage. The discriminative resolution among        multiple receivers relays on the dimensions of the distributed        platforms.

A composited transfer function (CTF) optimized under a finite number ofuser indexed performance constraints featuring a 1-to-m concurrentrelationship, and is a spatially sampled radiation pattern of anoptimally shaped beam viewed through a dynamic communication channeldominant by multiple paths. There are m spatially sampled outputs in aradiation pattern from an optimized BFN and only one common input to theBFN. In other words, this optimized function features integrated effectsof an optimally shaped beam cascaded by effects of multiple scatteringpaths in a propagation channel. The function is optimized under the userindexed performance constraints via a selected optimization algorithm.

Composited transfer functions shaped for enhanced isolations amongmultiple users will have distinct responsive features to various users.For a two-user MIMO example in a multipath dominated environment; afirst set of parallel preprocessors for transmission in a hub mayfeature composited transfer functions (CTFs), characterizing propagationpaths from the inputs of the pre-processors all the way to variouselements of the two user antennas, with “high” intensity responses toantenna elements of a first users while concurrently showing “low”intensity responses to a second users. Similarly, a second set ofpreprocessors may feature complex transfer functions (CTFs) with “low”intensity responses to all antenna elements of the first users whileconcurrently showing “high” intensity responses to those of the secondusers.

Outputs of two conventional MIMO processors, one for the first user andthe other for the second user, are respectively connected to the inputsof the two sets of the preprocessors. The multiple outputs of thepre-processors are then connected to the same suite of the transmittingantenna elements. As a result, spectrum can be reused multiple times forbetter spectrum utility efficiency.

Our receiver design concepts include techniques incorporating multipleantenna elements and using space-time-frequency adaptive processing.Coordinated multi-user communication networks coordinate and/or combinesignals from multiple antenna elements or base stations to make itpossible for mobile users to enjoy consistent performance and qualitywhen they access and share videos, photos and other high-bandwidthservices, whether they are close to the center of their serving cell orat its outer edges. One issue with these networks is that conventionalchannel quality feedback schemes do not take into account a reduction ininterference that can be achieved by coordination. Thus, there aregeneral needs for these networks and methods for beamformingcoordination that take into account the reduction in interference thatresults from the coordination of the base stations. There are alsogeneral needs for channel quality feedback schemes suitable forinterference suppression in a coordinated multi-user network.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1a illustrates a communication network in a multipath dominatedpropagation environment with antenna diversity. The multipaths arecreated via airborne platforms.

FIG. 1b illustrates a point-to-point (p-to-p) communication network in amultipath dominated propagation environment with a multiple-input andmultiple-output (MIMO) configuration in accordance with someembodiments. The multipaths are created via airborne platforms.

FIG. 1c illustrates a point-to-multiple point (p-to-mp) communicationnetwork via multiple airborne platforms; the foreground links 4200 arein L/S band and the background links 4500 are in X, Ku, Ka, or otherband.

FIG. 2a illustrates a point-to-point (p-to-p) MIMO scheme in accordancewith some embodiments; forming multiple independent links (on samefrequency channels) between a transmitter and a receiver to communicateat higher total data rates. The multipaths are created via airborneplatforms.

FIG. 2b illustrates a point-to-point (p-to-p) MIMO scheme in accordancewith some embodiments; forming multiple independent links (on samefrequency channels) between a transmitter and a receiver to communicateat higher total data rates, but there are cross-paths between antennaelements. The multipaths are created via airborne platforms.

FIG. 3a illustrates a point-to-multiple point (p-to-mp) MIMO scheme incharacterizing a multipath dominant propagation channel by measuringtransfer functions h_(ikj) from an ith transmitting element in atransmitter to a j^(th) receiving element of a k^(th) user elementsaccordance with some embodiments. The multipath dominated channelfeatures multiple transponding airborne platforms;

FIG. 3b illustrates an exemplified probing signal at transmitter, thatat a k1 receiving element, and that at the n2 element accordance withsome embodiments as shown in FIG. 3a . A spreading code Ci is depicted,and the multipath dominated channel features multiple transpondingairborne platforms;

FIG. 4a illustrates a scheme for a point-to-multiple point (p-to-mp)MIMO in characterizing a multipath dominant propagation channel bymeasuring composited transfer functions h_(baki) from an input port, ba,of a transmitting beam forming network (BFN) in a transmitter to aj^(th) receiving element of a k^(th) user. The multipath dominatedchannel features multiple transponding airborne platforms; A compositedtransfer function (CTF) is a linear combination of many point-to-pointtransfer functions

FIG. 4b illustrates an exemplified probing signal at transmitter, thatat a k1 receiving element, and that at the n2 element accordance withsome embodiments as shown in FIG. 4a . A spreading code Ci is depicted,and the multipath dominated channel features multiple transpondingairborne platforms;

FIG. 5 depicts signal flow diagrams for (a) a MIMO transmitter and (b) aMIMO receiver in accordance with some embodiments.

FIG. 6 illustrates a communication network in a multipath dominatedpropagation environment performing preprocessing to form two groups ofuser sensitive composited transfer functions in accordance with someembodiments; The multipath dominated channel features multipletransponding airborne platforms;

FIG. 7a depicts a flow diagram in generating optimized compositedtransfer functions via updated channel status information (CSI) andspecified beam shaping criteria for a MIMO transmitter in accordancewith some embodiments.

FIG. 7b depicts a more detailed flow diagram in generating compositedtransfer functions via updated channel status information (CSI) for aMIMO transmitter in accordance with some embodiments.

FIG. 8 illustrates a communication network in a multipath dominatedpropagation environment performing preprocessing to form two groups ofuser sensitive transferred functions assuming users featuring tworeceiving antenna elements each in accordance with some embodiments;

FIG. 9 illustrates a communication network in a multipath dominatedpropagation environment performing preprocessing to form two groups ofuser sensitive transferred functions assuming both users featuring tworeceiving antenna elements each in accordance with some embodiments. Oneuser also features wavefront multiplexing/demultiplexing for dynamicresource allocations among RF power and RF bandwidth resources of thetransmitting elements. The multipath dominated channel features multipletransponding airborne platforms;

FIG. 10 illustrates a MIMO communication network via multiple airbornetransponding platforms servicing two uses concurrently. Two groups ofuser sensitive transferred functions are formulated assuming both usersfeaturing two receiving antenna elements each in accordance with someembodiments.

FIG. 11 illustrates a MIMO communication network via multiple airbornetransponding platforms servicing two uses concurrently. Two groups ofuser sensitive transferred functions are formulated assuming both usersfeaturing two receiving antenna elements each in accordance with someembodiments. Ground based beam forming techniques are used to addressand direct signals to be radiated by identified elements on UAVs.

FIG. 12 illustrates a multi-user MIMO communication configuration in apropagation environment dominated by a fleet of multiple air bornetransponding platforms with preprocessing to form two groups oforthogonal beams in a common frequency slot dedicated for twoindependent users in accordance with some embodiments.

FIG. 13 illustrates a multi-user MIMO communication configuration in apropagation environment with two exclusive sets of airborne transpondingplatforms with preprocessing to form two groups of orthogonal beams in acommon frequency slot dedicated for two independent users in accordancewith some embodiments.

FIG. 14 illustrates a multi-user MIMO communication configuration in apropagation environment with 4 airborne transponding platforms. Thetransmitting site features a preprocessing of wavefront multiplexing (WFmuxing) and digital beam forming (DBF) while the receiving sites withpost processing of DBF and Wavefront de-multiplexing (WF demuxing). TheDBF's are form a groups of 4 orthogonal beams (OB) in a common frequencyslot, tracking and communicating with transponding platformsindividually. The four platforms are dedicated for two independent usersin accordance with some embodiments. The WF muxing/demuxing enabledynamic resource allocations among the two users, both in radiated powerand in channel bandwidth.

FIG. 15 illustrates a multi-user MIMO communication configuration withdigital beam forming (DBF) networks and Wavefront muxing/demuxing forboth transmitter or/and receivers in a multipath dominated propagationenvironment with preprocessing to form two groups of orthogonal beams,or beams with quiet-zones, in a common frequency slot dedicated for twoindependent users in accordance with some embodiments; There are 4transmitting beams and 8 airborne transponding platforms; eachtransmitting beam covers multiple platforms.

FIG. 16 illustrates a similar configuration as that in FIG. 15 for amulti-user MIMO communication with digital beam forming (DBF) networksand Wavefront muxing/demuxing for both transmitter or/and receivers in amultipath dominated propagation environment with preprocessing to formtwo groups of orthogonal beams, or beams with quiet-zones, in a commonfrequency slot dedicated for three independent users in accordance withsome embodiments; There are 4 transmitting beams and 8 airbornetransponding platforms; each transmitting beam covers multipleplatforms.

FIG. 17 illustrates an alternate multi-user MIMO communicationconfiguration with digital beam forming (DBF) networks and Wavefrontmuxing/demuxing for both transmitter or/and receivers in a propagationenvironment dominated by multiple airborne transponding platforms. Thetransmitting site features preprocessing to form two groups oforthogonal beams, or beams with quiet-zones, in a common frequency slotdedicated for two independent users in accordance with some embodiments;There are 4 transmitting beams and 8 airborne transponding platforms;each transmitting beam covers multiple transponding platforms.

FIG. 18 illustrates a multiuser MIMO communication configuration withmultibeam antenna (MBA) elements and Wavefront muxing/demuxing fortransmitter in a multipath dominated propagation environment withpreprocessing to form two groups of orthogonal beams, or beams withquiet-zones, in a common frequency slot dedicated for two independentusers in accordance with some embodiments; There are 4 transmittingbeams and 8 airborne transponding platforms; each transmitting beamcovers multiple platforms.

FIG. 19 illustrates a multiuser MIMO communication configuration withcombinations of direct radiating elements and multibeam antenna (MBA)elements and Wavefront muxing/demuxing for transmitter in a propagationenvironment dominated by multiple airborne transponding platforms. Thetransmitting site features with preprocessing to form two groups oforthogonal beams, or beams with quiet-zones, in a common frequency slotdedicated for two independent users in accordance with some embodiments;There are 4 transmitting beams and 8 airborne transponding platforms;two of the transmitting beams are low gain with wide angular coverage toreach all 8 platforms and the other two featuring high gain with narrowangular coverage for connecting subsets of the 8 platforms. The4-element antennas in various receivers shall feature at least 4independent beams. The WF muxing/demuxing scheme enable dynamic resourceallocations among the two users, both in radiated power and in channelbandwidth. These communications resources are aggregated from all 8transponding platforms.

FIG. 20 illustrates a multiuser MIMO communication configuration withcombinations of direct radiating elements and multibeam antenna (MBA)elements and Wavefront muxing/demuxing for transmitter in a propagationenvironment dominated by 8 airborne transponding platforms. Thetransmitting site features preprocessing to form multiple beams, orbeams with quiet-zones, in a common frequency slot dedicated for twoindependent users in accordance with some embodiments; The DBF isprogrammed to form two shaped beams from two transmitting elementsfeaturing low gain with wide angular coverage to reach all 8 platforms.The other two high gain beams with narrow angular coverage are orientedto connect subsets of the 8 platforms. The 4-element antennas in variousreceivers shall feature at least 4 independent beams. The WFmuxing/demuxing scheme enable dynamic resource allocations among the twousers, both in radiated power and in channel bandwidth. Thesecommunications resources are aggregated from all 8 transpondingplatforms.

FIG. 21 depicts a point-to-point (p-to-p) high bandwidth MIMOcommunications configuration with WF muxing via 4 transponding airborneplatforms which may be transponding UAVs.

FIG. 22 depicts a similar p-to-p MIMO configuration as that of FIG. 21with greater channel capacity. It is scaled via more transponding UAVsfor a broadband wireless communications pipe with a higher channelcapacity; say >100 GB per second.

FIG. 23 depicts another p-to-p MIMO configuration with WF muxing similarto that of FIG. 21 with greater channel capacity. It can be scaled for abroadband wireless communications pipe with a higher channel capacity.

FIG. 24 depicts a point-to-point (p-to-p) high bandwidth communicationsconfiguration with multiple channels with channel bonding via anon-coherent WF muxing via 4 transponding airborne platforms/UAVs. WFmuxing transforms are performed on data to be transmitted in a beforemulti-channel modulations. Similarly, WF demuxing are implemented onreceived data sets after demodulated on signals received from multiplechannels. This channel bonding configuration via WF muxing providesbetter data transport privacy and enhanced reliability via redundancy;but not higher signal-to-noise ratio (SNR).

FIG. 25 depicts a point-to-point (p-to-p) high bandwidth MIMOcommunications configuration with WF muxing via 4 satellites;

FIG. 26 depicts another p-to-p MIMO configuration similar to that ofFIG. 25 with greater channel capacity. It can be scaled for a broadbandwireless communications pipe with a higher channel capacity with moresatellite transponders.

FIG. 27 depicts a point-to-point (p-to-p) high bandwidth communicationsconfiguration with multiple channels with channel bonding via anon-coherent WF muxing via 4 transponding satellites. WF muxingtransforms are performed on data to be transmitted before multi-channelmodulations. Similarly, WF demuxing are implemented on received datasets after demodulated on signals received from multiple channels. Thischannel bonding configuration via WF muxing provides better datatransport privacy and enhanced reliability via redundancy; but nothigher signal-to-noise ratio (SNR).

FIG. 28 depicts a point-to-point (p-to-p) high bandwidth MIMOcommunications configuration with WF muxing via 4 transpondingsatellites and 4 transponding airborne platforms;

DETAILED DESCRIPTION

The following description and the drawings sufficiently illustratespecific embodiments to enable those skilled in the art to practicethem. Other embodiments may incorporate structural, logical, electrical,process, and other changes. Portions and features of some embodimentsmay be included in, or substituted for, those of other embodiments.Embodiments set forth in the claims encompass all available equivalentsof those claims.

Unmanned air platforms (UAVs), are used in most of the illustrations foractive scattering in a communications channel dominated by multipathpropagations. In many embodiments, other types of mobile or stationarytransponding platforms, including other air platforms, satellites, andthose ground or sea based stationary and mobile platforms, may beincorporated to substitute the transponding UAVs for active scatteringin a multipath dominated communications channel. Embodiments set forthin the claims also encompass all available equivalents of those claims.

FIG. 1a illustrates a point-to-point (p-to-p) communication network inaccordance with some embodiments. It shows the UAVs 120-1 and 120-2 and“bent-pipe” links from a transmitter 111 at a source on ground to areceiver 121 at a destination on ground via the UAVs in a communicationchannel 150. The communications system features a transmitter 111 at asource with a transmit antenna with diversity 114, and a receiver 121 ata destination with a receive antenna with diversity 124. The transmitter111 at the source comprises a digital signal processor (DSP) 111 and aradio 113 comprising a frequency up-converter, and power amplifiers, ortheir equivalents. The DSP 111 may perform additional coding and otherformatting functions on input signals which shall have already beenmodulated for transmission. The additional coding may includedemodulating and re-modulating with new codes, or simply adding codes onmodulated waveforms; e. g. OFDM. A propagation channel 150 comprisesmultiple transponding UAVs 120-1 and 120-2 in slow-moving flyingpatterns; such as in forms of small figures of “8” or small race tracks.The UAVs 120-1 and 120-2 feature receiving links covering thetransmitter 111 at the source, and transmitting links for the receiver121 at the destination. We also referred these UAVs as active scatteringplatforms in a multipath dominate channel 150.

Transponding payloads just like typical payloads for transpondingsatellites in C or Ku band, not shown, each of the UAVs features L orS-band transponders to receive signals in a first uplink frequency slot,f_(u1), radiated by the transmitter 111 on a ground source site. Thereceived signals on the UAV 120-1 are amplified by low noise amplifiers,and then properly filtered, frequency translated to a first down linkfrequency slot, f_(d1), power-amplified before re-radiated toward thereceiver 121 at a destination.

Referring to FIG. 1a , the receiver 121 comprises a radio 123 whichcomprising low noise amplifiers, frequency down-converters, digitizers,and a digital signal processor (DSP) 122 performing channel-decoding andother re-formatting functions. In MIMO terminology, this is calledSingle Input, Single Output (SISO). In information theory, theShannon-Hartley theorem tells the maximum rate at which information canbe transmitted over a communications of a specified bandwidth in thepresence of noise. The channel 150 comprises of two independent links inseries; an uplink from the transmitter 111 at a source location to UAVs,and a down link from UAVs to the receiver 121 at a destination. Thetheorem establishes Shannon's channel capacity for such a communicationlink, a bound on the maximum amount of error-free information that canbe transmitted with a specified bandwidth in the presence of the noiseinterference. According to Shannon, the capacity C of a radio channel150 is dependent on bandwidth B and the signal-to-noise ratio S/N whichshall include effects of both links. The following applies to a SISOsystem:

C=B log₂(1+S/N)  (1)

Conventional “Single Input Single Output” (SISO) systems were favoredfor simplicity and low-cost but have some shortcomings: (a) outageoccurs if receiving antennas fall into null, however, switching betweendifferent antennas 114 and 124 (among total four possibilities asdepicted in FIG. 1) can help in circumventing channel fading, (b)radiated power is wasted by sending signals in all directions from Omnidirectional transmitting antennas and will cause additional interferenceto other users; (c) sensitive to interference from all directions, and(d) total radiated power limited by output of a single power amplifier.

FIG. 1b depicts a Multiple Input Multiple Output (MIMO) system withmultiple parallel radios for single user. The system links a source to adestination through a communication channel with multiple activescattering UAV platforms, and features a transmitter 131 at the sourcewith a two transmit antennas 134, and a receiver 141 with two receiveantennas 124 at the destination. The transmitter 131 comprises a digitalsignal processor (DSP) 112 performing segmenting (or dividing),additional coding and other formatting functions on input signals whichhas been modulated, and a radio 113 comprising of a frequencyup-converter, and power amplifiers, or their equivalents. A propagationchannel 150 comprises multiple transponding UAVs 120-1 and 120-2 inslow-moving flying patterns; such as in forms of small figures of “8” orsmall race tracks. Each of the UAVs 120-1 and 120-2 feature receivinglinks covering the transmitter 111 at the source, and transmitting linksfor the receiver 121 at the destination. The receiver 141 comprises aradio 123 consisting low noise amplifiers, frequency down-converters,and demodulators; and a digital signal processor (DSP) 142 performingdecoding, de-segmenting (or combining), and other re-formattingfunctions.

MIMO systems with multiple parallel radios in general improve thefollowing; (a) outages due to dynamic fading are reduced by usinginformation from multiple antennas, (b) total transmit power areincreased via multiple power amplifiers, (c) higher throughputs arepossible, and (d) transmit and receive interference can be limited bymany techniques.

The MIMO system in FIG. 1b consists of n (n=2) transmit and m (m=2)receive antennas. By using the same channel 150 as that in FIG. 1a ,every receiving antenna 124 receives two leaking components intended forthe other antenna. The connection from antenna 1 of the transmitterantennas 134 through a communication channel 150 to antenna 1 of thereceiver antennas 124 is specified with h₁₁, etc., while the leakingconnections from antenna 1 of the transmitter antennas 134 via thecommunication channel 150 to antenna 2 of the receiver antennas 124 isidentified as cross component h₂₁, etc. There is a transmission matrix;∥H∥ with the dimensions n×m, or 2×2 for FIG. 1b ;

$\begin{matrix}{{H} = {\left\lbrack {\begin{matrix}h_{11} \\h_{21}\end{matrix}\begin{matrix}h_{12} \\h_{22}\end{matrix}} \right\rbrack.}} & (2)\end{matrix}$

The following transmission formula results from receive vector y,transmit vector x, and noise n;

y=Hx+n.  (3)

To characterize the propagation effects in the multipath dominantcommunications channel 150 from a first one of the radiating elements134 of the transmitter 131 to a first one of the receiving elements 124of the receiver 141, a transfer function h₁₁ is a result of followingtwo parallel paths; (1) path 1 from the first radiating element 134 tothe first UAV 120-1 followed by a link to the first receiving element124, and (2) path 2 from the first radiating element 134 to the secondUAV 120-2 followed by a link to the first receiving element 124.Similarly, each of the other three transfer functions, h₂₁, h₁₂, andh₂₂, are results of two parallel propagating effects through the twoUAVs 120-1 and 120-2. If there were M UAVs, each of the 4 four transferfunctions (h₁₁, h₂₁, h₁₂, and h₂₂) should become results of effects fromparallel propagating paths through the M UAVs.

Data to be transmitted is divided into independent data sub-streams. Thenumber of sub-streams M is always less than or equal to the number ofradiating or transmitting antennas. In the case of asymmetrical (m # n)antenna constellations, M is always smaller or equal the minimum numberof antennas. For example, a 4×4 system could be used to transmit four orfewer streams, while a 3×2 system could transmit two or fewer streams.Theoretically, the capacity C increases linearly with the number ofstreams M

C=M B log₂(1+S/N)  (4)

When the individual streams are assigned to various users, this iscalled Multi-User MIMO (MU-MIMO). This mode is particularly useful inthe uplink because the complexity on the UE side can be kept at aminimum by using only one transmit antenna. This is also called‘collaborative MIMO’. Cyclic delay diversity (CDD) introduces virtualechoes into OFDM-based systems. This increases the frequency selectivityat the receiver. In the case of CDD, the signals are transmitted by theindividual antennas with a time delay. Because CDD introduces additionaldiversity components, it is particularly useful as an addition tospatial multiplexing.

Spatial diversity comprises receiving (Rx) and transmitting (Tx)versions. The purpose of spatial diversity in FIG. 1a is to make thetransmission more robust. There is no increase in the data rate. Thismode uses redundant data on different paths.

Rx diversity uses more antennas on the receiver side than on thetransmitter side. A simple scenario consists of two Rx and one Txantenna (SIMO, 1×2). Because special coding methods are not needed, thisscenario is very easy to implement. Only two RF paths are needed for thereceiver. Because of the different transmission paths, the receiver seestwo differently faded signals. By using the appropriate method in thereceiver, the signal-to-noise ratio can now be increased. Switcheddiversity as shown in FIG. 1 a always uses the stronger signal, whilemaximum ratio combining uses a summed signal from the two signals. Onthe other hand for Tx diversity, there are more number of Tx than thatof Rx antennas. A simple scenario uses two Tx and one Rx antenna (MISO,2×1). The same data is transmitted redundantly over two antennas. Thismethod has the advantage that the multiple antennas and redundancycoding is moved from the mobile UE to the base station, where thesetechnologies are simpler and cheaper to implement.

To generate a redundant signal, space-time codes may be used. Alamoutideveloped the first codes for two antennas in 1998, and reported resultson IEEE Journal on Select Areas in Communications, Vol. 16, No. 8,October 1998. Space-time codes additionally improve the performance andmake spatial diversity usable. The signal copy is transmitted not onlyfrom a different antenna but also at a different time. This delayedtransmission is called delayed diversity. Alamouti's space-time codescombine spatial and temporal signal copies as followed;

The signals s₁ and s₂ are multiplexed in two data chains. After that, asignal replication is added to create the Alamouti space-time blockcode.

FIG. 1c depicts a MU-MIMO system serving 3 users 1301, 1302, and 1303via a communications channel 150 with 3 transponding UAVs 120-1, 120-2,and 120-3 for some embodiments. The 3 users are in a common service area130 by all three UAVs 120 via foreground links 4200 in L/S bands, whilea communications hub 410 is connected to all three UAV's 120-1, 120-2and 120-3 via feeder-links 4500 at X, Ku, Ka, or other bands.

In other embodiments, air platforms may functions as repeaters. In thosecases, the down link frequency slot, f_(d1), for the re-radiated signalswould be at same as the uplink frequency slot; f_(u1). These frequencyslots may be in commercial cell phone bands. However, the repeatersshall be on large UAVs, which can adequately separating receiving andtransmitting apertures physically to avoid positive feedbacks causingself-oscillating in the repeater.

In some additional embodiments (not shown), two transponding airplatforms may be cascaded to function as a repeater. In those cases, afirst air platform shall feature a uplink at and a “crosslink” frequencyslot, f_(x), for the re-radiated signals; while a second transpondingair platform feature a cross link input at f_(x), and re-radiationfrequency for down link, at f₁; where f₁ shall be in commercial cellphone band, and f_(x) in cross links may be in X, Ku, Ka or othermillimeter, or optical bands. As a result, a transmitted signal streamradiated by a source on ground will be linked to the first air platformat f₁, re-radiated toward the second platform at f_(x), captured by thesecond platform and re-radiated toward a user at the destination at f₁again.

Referred back to FIG. 1c , the ground facility 410 via multiplexedfeeder links 4500 feature (1) directional high gain antennas 411tracking and communicating with UAVs 120 individually, (2) a ground basebeam forming (GBBF) 412 capability to deliver different signal streamsto various radiators for foreground communications on any one of theUAVs 120 in transmit and to recover different signal streams fromvarious receiving elements for foreground communications on any one ofthe UAVs 120 in receiving, and (3) an interface or a gateway via itsfunction as a mobile hub 413 to external networks 480.

In other embodiments, the antennas for the ground hub 410 may comprisearray elements. There may not be GBBF 412 functions, but otherequivalents to deliver forward link signals and receive return linkssignals to and from groups of array elements on board UAVs servicingusers in foreground coverage areas. In some embodiments, the foregroundcoverage via foreground links and the background coverage via feederlinks are significantly overlapped. In some other embodiments, thefeeder links for background coverage feature the same frequency bands offoreground links.

Spatial multiplexing in MIMO as depicted in FIG. 2a is not intended tomake the wireless transmission more robust; rather it increases the datarate. As depicted, the DSP 232 comprises two portions; a segmentingdevice 135 and two signal processors (SP) 1321. Input signal stream isdivided or segmented by a segmenting device, or a splitter 135 into 2separated substreams; which are to be transmitted independently via 2separate antennas 134 after being additional coded and formatted (e.g.such as space-time coding) by the SP 1321, frequency up-converted, andthen power amplified by radios 133.

At a destination with a receiver 141, the two antennas 144 will capturethe two separated signal substreams independently. In a simplified andidealized scenario, a first one of the two antennas 144 will onlyrespond to a first signal sub stream sent by a first of the twotransmitting antennas 134; while a second one of the two antennas 144will only respond to a second signal substream sent by a second one ofthe two transmitting antennas 134. The received signal substreams willthen be properly conditioned by the radios 143 before being reformattedand decoded (e.g. such as space-time decoding) by the signal processors(SP) 1421 and then de-segmented by a combining device 145. The radios143 perform, among other functions, low noise amplification, andfrequency down conversion. The functions of SP 1421 and combiner 145 areparts of functions of DSPs 142.

However, there are cross-paths between antennas in real world. BecauseMIMO transmits via the same channel 150, transmissions with crosscomponents not equal to 0 will mutually influence one another asdepicted in FIG. 2b . The first of the two receiving antennas 144 willalso respond to the second data stream sent by the second antenna.Similarly, the second of the two receiving antennas 144 will alsorespond to the first data stream sent by the first of the twotransmitting antennas 134. When strong effects of cross-paths occur, thereceived signals by the two received antennas 144 shall exhibit highcross-correlation. On the other hand, when effects of cross-pathsbecoming weak; so will the cross correlations among the two receivedsignal or data streams. The cross correlations must be minimized viaoptimization algorithms, which may be implemented by signal processors(SP) 1421. In other words, the correlation among the two receivedsubstreams must be decoupled before a de-segmenting, summing, or mergingdevice 145. As indicated without a decoupling processing in the two SPs1421, the output of the de-segmenting device 145 for the two receivedsignal substreams will be a received signal stream with highself-interference due to multipaths.

FIG. 3a illustrates a MIMO scheme in characterizing a multipath dominantpropagation channel by measuring transfer functions h_(ijk); from ani^(th) transmitting element 134 in a transmitter to a j^(th) receivingelement 144 of a k^(th) user in accordance with some embodiments. Themultipath dominant channel 150 comprises active scattering from 4 UAVs120. A probing signal 251, Pb_(i)(t), is encoded by an encoder 238 and aspreading code 258, before sent to various user elements by an i^(th)one of the n transmitting elements 134. The encoded signals afterpropagating through a multipath dominated propagation channel 150, andarriving at various receiving elements; k1 through n2. The receivedprobing signals after properly conditioned (low-noised amplified,filtered, frequency down converted, and digitized will be send tovarious decoders, 258-k 1 to 258-n 2, which performing de-spreadingprocessed. Propagations from a source to a destination, such as fromelement 1 of the transmitter array 134 to the decoder 258-n 2 forelement 2 of the receiving array 144 of the n^(th) user, feature atleast 4 active paths in the communication channel 150; (1) a first pathvia a first UAV 120-1, (2) a second one via a second UAV 120-2, (3) athird one via a third UAV 120-3, and (4) a fourth one via a fourth UAV120-4, respectively. Therefore, the transfer function h_(1n2) representsa propagation characteristics of combining effects of the 4 parallelpropagation paths from element 1 of the transmitting array 134 toelement 2 of the array 144 for the n^(th) user.

FIG. 3b depicts an example of a probing signal 251 at the transmittersource. The probing signal is modulated by a spreading code C_(i) 258.After propagating through the multipath channel 150, received probingsignals 251-k 1 and 251-n 2 feature multipath propagation effects inboth I and Q channels representing time delays, phase and amplitudeeffects. In-phase and quadrature-phase components of the receivedprobing signals for first element of the k^(th) receiver radiated by thei^(th) transmitting element are depicted as (I_Pb_(ik1)(t),Q_Pb_(ik1)(t)), and those for second element of the n^(th) receiver areindexed as (I_Pb_(in2)(t), Q_Pb_(in2)(t)).

FIG. 4a illustrates a beam forming scheme for MIMO in characterizing amultipath dominant propagation channel by measuring a compositedtransfer functions h_(bakj); which is defined from an input port, ba, ofa transmitting beam in a transmitter to a j^(th) receiving element of ak^(th) user, where “a” represents one of the integer 1, 2, 3, or 4. Acomposited transfer function (CTF) is generated by a linear combinationof various conventional transfer functions from different i^(th)transmitting elements to a set of same receiving elements (i.e bysumming over all the properly weighted i's). The function which performsa linear combination over a transmitting array with n antenna elementsof is a 1-to-n beam forming network (BFN). The associated weightingparameters to various transfer functions are a weighting vector,referred as beam-weighting vector (BWV). By changing the BWV, theassociated radiating pattern of an updated beam by the BFN is alteredaccordingly. With n-elements, the radiating pattern from an array can beoptimized or shaped to meet precisely up to n independent performanceconstraints; including forming beam peaks and nulls at thoseconstraining directions or locations of receiving elements which pickingup integrated effects of multi-path scattered signals radiated by thetransmitting beam.

In other words, the transmitting beam with a set of optimized BWV in aBFN feature a unique wavefront generated by concurrent radiations frommultiple transmitting elements. The wavefront after propagating throughthe multipath dominated channel arrives at various destinations shallexhibit amplitude and phase distributions which shall fulfill a set ofperformance constraints concurrently. Various M BFNs via a same set ofradiating elements shall produce M different beams concurrently. Eachshall feature a unique and independent wavefront under a set of uniqueperformance constraints. The M wavefronts will go through the samemultipath dominated channel and reach to various receivers withspecified performance constraints concurrently.

On the other hand, optimized radiation patterns with n components of aBWV may be shaped to meet more than n-constrained performance.Performance constraints may also be specified preferred coverage zonesand rejection zones or quiet zones. Over a specified quiet zone, theintensity levels of radiated signals by the shaped beam after scatteredby a multipath dominated channel are below a pre-determined thresholdwith low intensity levels; usually a −35 to −50 dB below the levels ofcoverage zones.

A probing signal 251 depicted in FIG. 4b , Pb_(ib)(t), is encoded by anencoder 238 with a spreading code 258 also depicted in FIG. 4b , beforesent to an input of a beam forming network (BFN) 239 for the i^(th)beam, with multiple transmitting elements 134. A beam weight vector 239a (BWV) is optimized under a set performance constraints (not shown).The probing signals are then radiated to a multipath dominatedpropagation channel 150. As a result, a unique wavefront is generatedand propagating toward various user elements through the multipathdominated channels. The encoded signals after propagating through amultipath dominated channel 150, and arriving at various receivingelements; k1 through n2, are captured by these elements 144individually. The received probing signals after properly conditioned(low-noised amplified, filtered, frequency down converted, and digitizedwill be send to various decoders, 258-k 1 to 258-n 2, which performingde-spreading processed. The received probing signals 251-k 1 to 251-n 2depicted in FIG. 4b feature multipath propagation effects in both I andQ channels representing time delays, phase and amplitude effects. Forthis example the desired coverage zone is set for the k^(th) receiver,therefore, received optimized probing signals in I/Q format by the k1element depicted in the insert 251-k 1 feature high intensities ofmultiple pulses. On the other hand, a rejection zone or a quiet zone isassigned to an n^(th) receiver. As a result, received optimized probingsignals in I/Q format by the second receiving element of the n^(th)receiver after decoded by a decoder 258-n 2 feature extremely lowintensities of multiple pulses as depicted.

The active scattering effects from the UAVs 120 are “integrated” as apart of a scattering matrix with matrix components, h_(ijk), tocharacterize dynamic propagations between a i^(th) transmitting elementof the transmitter to a j^(th) receiving element of the k^(th) receiver.As the UAVs hover slowly over a service area, these matrix components,h_(ijk), will alter accordingly. The associated BWV's for optimizedshaped beams must be updated continuously in order to fulfill theprescribed performance constraints, which shall be indexed according touser identifications.

FIG. 5 depicts signal flow charts of typical MIMO systems for singleusers; a top panel for MIMO transmitters 311 a bottom panel for MIMOreceivers 321. There are feedback networks (not shown) for dynamicupdating the channel state information (CSI). As depicted in the toppanel 311 for a typical MIMO transmitter, an input signal stream issegmented by a stream splitter 312 into multiple parallel substreamsafter source-coded by a forward error correction (FEC) device 313. Thesubstreams after modulated by a bank of modulators 314 will be spatiallymapped into different combinations of transmit antenna indices at eachtime instance via a spatial mapping device/block 315. To convertspace-time streams (STS) into transmit chains (TC), a spatial mappingblock may be implemented via, among many other techniques, (1) directmapping, a 1-to-1 mapping from STS to TC; (2) spatial expansion,additional multiplication with a matrix for cases such as two STS andthree Tx antennas; (3) beam forming, additional multiplication with asteering vector; and (4) subcarrier mapping. Multiple parallel outputsfrom the spatial mapping block 315 for a transmitting antenna areconverted to a TC format by devices such as IFFT blocks 316 beforefrequency up-converted and power amplified by RF blocks 317. Variousamplified signals are then radiated by different transmitting antennas(not shown).

As depicted in the bottom panel 321 of FIG. 5, multiple receive signalscaptures by various Rx antennas are conditioned properly individually byRF frontends 327 which may comprise low-noise-amplifiers, and frequencydown-converters. At baseband digital format, the received substreams arechannelized by FFT processors 326; and the channelized signals areequalized and spatially unmapped into STS signals by a MIMO equalizer325. After demodulated by demodulators 324 and merged into singlestreams by de-segmenting devices 322, the recovered STS signals aredecoded by a decoder 323 and become reconstituted original data.

FIG. 6 depicted how to formulate composited transfer functions of apoint-to-2 point (p-to-2p) communications system featuring a transmitter431 at a source with 3 transmitting (Tx) elements 434, T1, T2, and T3,sending 2 signal streams independently through a multipath dominatedcommunication channel 150 to two different receivers Rx A 441 a at afirst destination and Rx B441 b at a second destination. The multiplepath dominated channel 150 comprises multiple UAVs 120 as activescattering platforms. A first signal stream, stream A, aiming for the RxA 441 a is divided into two segments; A1 and A2 substreams, in a firstof two DSPs 432. Following the first of the DSPs 432, A1 substream willbe connected to a first input of a first 2-to-3 beam forming network(BFN) 439 for a first shaped beam. Concurrently, A2 substream isconnected to a second input of the first 2-to-3 beam forming network(BFN) 439 for a second shaped beam. The three combined outputs for thetwo shaped beams from the first 2-to-3 BFN 439 are frequencyup-converted, and amplified by Radios 433 and radiated by threetransmitting elements 434. Signal substreams of A1 and A2 radiated bythree transmitting elements 434 organized via two transmitting shapedbeams shall feature two independent radiation patterns, or wavefronts.After actively scattered by the 4 UAVs 120 in a propagation channel 150,these radiation patterns or wavefronts shall deliver transmitted signalswith discriminative features; low intensities of flux densities ofradiated A1 and A2 signal substreams for the second receiver Rx B 411 bat the second destination, and high intensities of radiated A1 and A2signal substream flux densities for the first receiver Rx A 441 a overthe first destination. Furthermore, the first shaped beam shall aim formaximizing the signal flux density of A1 substream over the firstelement Ra1 of the receiving elements 444 a, while the second shapedbeam shall aim for maximizing the signal flux density of A2 sub streamover the second element Ra2 of the receiving elements 444 a.

We shall refer to a radiation pattern of a shaped beam for a transmittedsignal as a wavefront for the transmitted signal. A wavefront of ashaped beam radiated by the transmitting elements 434 is optimallysynthesized (not shown) by a beam forming mechanisms in one of the BFN439 under a set of performance constraints formulated by a compositetransfer function. The optimization (not shown) is identical toprocedures for shaped beam antennas under various discriminativeperformance constraints favoring one user and against others. There aretwo wavefronts associated to two shaped beams by the first 2-to-3 BFN439. We shall present formulation of composited transfer functions laterin this section.

Similarly a second signal stream, B stream, aiming for Rx B 441 b isalso divided into two segments; B1 and B2 substreams in a second 2-to-3BFN 439. Furthermore, B1 substream will be connected to a first input ofa second 2-to-3 BFN 439 for a third shaped beam. Concurrently, B2substream is connected to a second input of the second 2-to-3 BFN 439for a fourth shaped beam. The 3 common outputs of the third and thefourth beams, or the 3 outputs from the second 2-to-3 BFNs 439, arefrequency up-converted, and amplified by Radios 433 and radiated by thesame three transmitting elements 434. The optimization (not shown) isidentical to the procedures for the first two shaped beams by the firstBFN 439. There are two optimally shaped wavefronts associated to thethird and the fourth shaped beams by the second 2-to-3 BFN 439.

Signals radiated by the third and the fourth shaped beams via the threetransmitting elements 434, and after actively scattered by the 4 UAVs120, shall exhibit discriminative features; low intensities of radiatedflux densities of B1 and B2 signal substreams for the first receiver RxA at the first destination, and high radiated flux densities for thesecond receiver over the second destination. Furthermore, the thirdshaped beam shall aim for maximizing the signal flux density of B1substream over the first element Rb1 of the receiving elements 444 b,while the fourth shaped beam shall aim for maximizing the signal fluxdensity of B2 substream over the second element Rb2 of the receivingelements 444 b.

The first receiver Rx A 441 a features two Rx element Ra1 and Ra2 444 ato capture a first of two radiated signal streams by the transmitter 431dedicated for the first receiver Rx A. Concurrently, the second receiverRx B 441 b featuring two Rx element Rb1 and Rb2 444 b will capture asecond radiated signal stream by the transmitter 431 dedicated for thesecond receiver Rx B.

The p-to-2p MIMO communications systems in FIG. 6 will deliver signalsfrom a common source 431 to two separated destinations 441 a and 441 b;each with two receipted elements concurrently. Signal substreams A1 andA2 will be delivered only to and captured by antenna elements in Rx A441 a, while signal substreams B1 and B2 only to antenna elements of RxB 441 b. There are also feedback networks (not shown) for dynamicupdating the channel state information (CSI). Both the DSPs 432 at thesource 431 and the DSPs 442 a and 442 b at the respective destinations441 a and 441 b are used for additional directional mapping andde-mapping. With robust feedback networks in some embodiments,directional mapping/de-mapping are all done as preprocessing at a source431 so that correlations among received signals by individual receivingelements at a destination become minimized. As a result, low costterminals with limited processing capability can be used in a MIMOnetwork. On the other hand, with some capability in feedback channels inother embodiments, directional mapping/de-mapping are done aspost-processing at destinations 441 a and 441 b, respectively, tominimize correlations among received signals by individual receivingelements in a user device with high processing capability.

CSI is organized as transfer functions; h_(ik) characterizingpropagation features a set of multiple propagation paths from a i^(th)element of a transmitter to a k^(th) element of a receiver. For acommunications systems with m antenna element in transmit and N elementsin receive the transfer functions can be represented by a M×N transfermatrix, ∥H∥.

It is noticed that the transfer functions/matrixes characterizingpropagation channels feature parameters indexed by user's antennaelements, neither in forms of locations as lengths in a Cartesiancoordinates nor in direction as angles in a spherical coordinates. Moreprecisely, they are specified or indexed by antenna elementidentifications (IDs) of various users. We shall refer theseidentification conventions as “user ID indexed” or simply as “userindexed” in this application. Therefore, the phrase of “user indexedperformance criteria” means performance criteria at locations identifiedby ID of user element, and/or user ID. A user indexed transfer functionh_(ik) represents a transfer function between the i^(th) elements of atransmitting array to the k^(th) element of a receiver.

In this disclosure, many transfer functions have been indexed bysubscripts with three symbols. A component (h_(ijk)) has been used tocharacterize propagation features of channel characteristics from i^(th)element of a transmitter via set of multiple propagation paths to ak^(th) element of a j^(th) receiver.

Many conventional antenna synthesis designs and methods featureoptimizations in beam shaping techniques for a transmitting array withmultiple transmitting antenna elements in formulating a shaped beamradiation pattern as a weighted sum of radiation patterns of individualantenna elements. Furthermore the optimization process is to find a setof the weighting parameters of the individual element radiation patternsso that the performances of the optimized shaped beam fulfill a set ofpredetermined performance constraints. Both the radiation patterns ofshaped beams and associated performance constraints are specified asfunctions of angles in various coordinates. The shaped beam with aunique wavefront will radiate a signal stream to various directions inspace according to its radiation pattern.

However, measurements of known probing signals from the shaped beam ondiscrete locations, or spatially sampled points, in a common coverageregion for receivers, such as receiving elements of multiple receivers,may be used for optimizing the shaped beam so that the radiatedwavefront at those discrete locations meet prescribed performancecriteria, which are specified as functions of user indexes, not asfunctions of directions or angles. The performance constraints on theseselected locations are characterized as a point-to-multipoint (p-to-mp)composited transfer function in transmitter. These measurements; fromthe input of a shaped beam in a transmitter to multiple receivingelement locations of various sets of user equipment (UE), do include (1)discriminative effects of radiation pattern of the shaped beam, and (2)multipath active scattering effects by the UAVs 120 in a dynamiccommunication channels 150.

In some embodiments, we will incorporate concepts of orthogonal beams(OB) at the transmit side as performance constraints; forming two groupsof shaped beams, which are injected into a multipath dominant channel150. Instead of using line-of-sight directions as constraint parametersin beam shaping optimization; we use components of a scattering matrix,known as transfer functions, h_(ij), characterizing time delays,amplitude attenuations, and phase delays from the i^(th) elementposition in a transmitter via a set of multipaths of the channel 150 tothe j^(th) position in a receiver. The first sets of shape beams willfeature beam peaks toward first receiver and nulls toward the secondreceiver, while the second sets of shape beams with beam peaks towardthe second receiver and nulls toward the first receiver. These two setsare “orthogonal” to one another. A shaped beam is constrained by acomposited transfer function (CTF), which is a linear combination of thetransfer functions h_(ik), for all i's; where i is an index of thei^(th) transmitting element. A composited transfer function (CTF),constrained by a set of functions on multiple locations indexed by IDsof user elements instead of directions, features a unique wavefrontcharacterizing effects of propagation from the input of a beam formingnetwork (BFN) of a shape beam all the way to various elements onreceivers from multiple sets of user equipment, respectively.

In other embodiments, we will incorporate performance constraints of“quiet zones” at the transmit side; forming two groups of beams. Forthis example of a p-to-2p configuration, two sets of shaped beams willbe formed at the transmission side taking advantage of a multipathdominant communications channel 150. Instead of line-of-sight directionsas constraint parameters in beam shaping optimization; we will usecomponents of a scattering matrix, known as transfer functions h_(ij),characterizing time delays, amplitude attenuations, and phase delays inpropagation via a set of multipaths from the i^(th) position in atransmitter to the j^(th) position in a receiver. The first sets willhave shape beams with beam peaks toward first receiver and “quiet zones”toward the second receiver, while the second sets will have shape beamswith beam peaks toward the second receiver and “quiet-zone” toward thefirst receiver.

“Quiet zone” criteria are different from those of “nulling.” Over“selected” quiet zones the associated transfer functions, the signalflux densities for a desired signal stream will be below a predefinedthreshold value; which shall be −20 or −30 dB below those at the beampeaks of shaped beams. Beam shaping constraints via quiet zones are setfor low intensity values of desired signal flux densities on compositedtransfer functions over a region, while those for OB are set for zeroresponses on desired signal flux over specified locations only.Feed-back information for quiet zone shall be from line integrations ofreceived powers of selected signals over many in situ point sensors orreceived power of selected signals from line-sensors; while that for OBperformance constraints shall be from received power of selected signalsfrom point-sensors.

Let us define h_(iax) as the scattering matrix component from a Tielement of a transmitter to the k^(th) element of the Ra receiver, Rak,where i=1, 2, or 3 and k=1, or 2. Similarly, h_(ibx) as the scatteringmatrix component from the Ti element to the k^(th) element of the Rbreceiver, Rbk, where i=1, 2, or 3 and k=1, or 2. A first beam formingmechanism for a beam B_(a1) is resided in a first 2-to-3 BPFs 439. Thesignal substream A1, to be radiated by the beam B_(a1), is connected toa first beam port, BP_(a1), a first input of the first 2-to-3 BFN 439.

A composited transfer function (CTF), H_B_(a1), from the beam portBP_(a1) (a source point) to a set of receiving elements,

$\quad\begin{bmatrix}{{Ra}\; 1} \\{{Rb}\; 1} \\{{Rb}\; 2}\end{bmatrix}$

(multiple destination points), is defined as a linear combination of[T1], [T2] and [T3]; where [Ti] is the scattering matrix, a set oftransfer functions, from the i^(th) transmitting element to the set ofreceiving elements

$\begin{bmatrix}{{Ra}\; 1} \\{{Rb}\; 1} \\{{Rb}\; 2}\end{bmatrix}.$

More specifically, the composited transfer function (CTF) is expressedas:

$\begin{matrix}\begin{matrix}{{H\_ B}_{a\; 1} = {{{wa}\; 1*\left\lbrack {T\; 1} \right\rbrack} + {{wa}\; 2*\left\lbrack {T\; 2} \right\rbrack} + {{wa}\; 3*\left\lbrack {T\; 3} \right\rbrack}}} \\{= {{{wa}\; {1\begin{bmatrix}{h\; 1\; a\; 1} \\{h\; 1b\; 1} \\{h\; 1b\; 2}\end{bmatrix}}} + {{wa}\; {2\begin{bmatrix}{h\; 2\; a\; 1} \\{h\; 2b\; 1} \\{h\; 2b\; 2}\end{bmatrix}}} + {{wa}\; {3\begin{bmatrix}{h\; 3\; a\; 1} \\{h\; 3b\; 1} \\{h\; 3b\; 2}\end{bmatrix}}}}} \\{= \begin{bmatrix}{{{wa}\; 1*h\; 1\; a\; 1} + {{wa}\; 2*h\; 2\; a\; 1} + {{wa}\; 3*h\; 3\; a\; 1}} \\{{{wa}\; 1*h\; 1\; b\; 1} + {{wa}\; 2*h\; 2\; b\; 1} + {{wa}\; 3*h\; 3\; b\; 1}} \\{{{wa}\; 1*h\; 1\; b\; 2} + {{wa}\; 2*h\; 2\; b\; 2} + {{wa}\; 3*h\; 3\; b\; 2}}\end{bmatrix}}\end{matrix} & (5)\end{matrix}$

We define the following components for the composited transfer functionfor beam B_(a1); (1) h_(ba1-b1) from the beam port BP_(a1) to Rb1, (2)h_(ba1-b1) from the beam port BP_(a1) to Rb1, and (3) h_(ba1-a1) fromthe beam port BP_(a1) to Ra1. For OB beam shaping; beam B_(a1) shallfeature “zero” responses or nulls at both Rb1 and Rb2 elements; asspecified in constraints 1 and 2:

h _(ba1-b1) =wa1*h1b1+wa2*h2b1+wa3*h3b1=0;  (6a)

h _(ba1-b2) =wa1*h1b2+wa2*h2b2+wa3*h3b2=0.  (6b)

Beam BBa1 shall also feature a peak at Ra1 location with constraint 3

Max(abs(h _(ba1-a1)))=Max(abs(wa1*h1a1+wa2*h2a1+wa3*h3a1)),  (6c)

-   -   where Max (x) is an operation to maximize x.

With three equations of 6a, 6b and 6c, an optimization algorithm shallled us to an optimum set of solutions for wa1, wa2 and wa3 as theoptimized weighting components of a beam weighting vector (BWV) for thefirst beam, B_(a1), under the above three constraints of OB beams.

Various optimization algorithms shall provide different solutions forthe weighting component; wa1, wa2, and wa3. Optimized solutionsfull-filling the OB beam shaping must meet all 3 constraints, (6a, 6band 6c) concurrently.

We may define the following components for the composited transferfunction for beam B_(a1); (1) h_(ba1-b1) from the beam port BP_(a1) toRb1, (2) h_(ba1-b1) from the beam port BP_(a1) to Rb1, and (3)h_(ba1-a1) from the beam port BP_(a1) to Ra1. For “quiet-zone” beamshaping; beam B_(a1) shall feature low response of the compositedtransfer functions at Rb1 and Rb2 with constraints 4 and 5

abs(h _(ba1-b1))=abs(wa1*h1b1+wa2*h2b1+wa3*h3b1)<δ1  (6d)

abs(h _(ba1-b2))=abs(wa1*h1b2+wa2*h2b2+wa3*h3b2)<δ1  (6e)

Where δ1 is a small positive number. Beam B_(a1) shall still feature apeak at Ra1 location with constraint 3

Max(abs(h _(ba1-a1))=Max(abs(wa1*h1a1+wa2*h2a1+wa3*h3a1)),  (6c)

-   -   where Max (x) is an operation to maximize x. In general, δ1        shall be less than −20 dB below the radiation level at the beam        peak; or (δ1)²<(h_(ba1-a1))2/100.

With three equations of 6c, 6d and 6e, an optimization algorithm shallled us to an optimum set of solutions for wa1, wa2 and wa3 as theoptimized weighting components of a beam weighting vector (BWV) for beamB_(a1) under the constraints of “quiet zone”. However, there may be moreconstraint locations with low flux density responses on the compositedtransfer functions over the receiving apertures of the second receiverin addition to Rb1 and Rb2. Adding more constraints will result inincreased dimension of associated beam weight vectors (BWVs).

In other embodiments, there are 4 spatial-sampling points in the seconddestination; Rb1, Rb2, Rb3 and Rb4. We may define the following twoadditional components for the composited transfer function for beamB_(a1); 1) h_(ba1-b3) from the beam port BP_(a1) to Rb3, (2) h_(ba1-b4)from the beam port BP_(a1) to Rb3. In other similar embodiments, theconstraints 4 and 5 can be re-written as

Abs(h _(ba1-b1))+Abs(h _(ba1-b2))+Abs(h _(ba1-b3))<δ1  (6d-1)

Abs(h _(ba1-b1))+Abs(h _(ba1-b4))<δ1  (6e-1)

Various optimization algorithms shall provide different solutions forthe weighting component; wa1, wa2, and wa3. The optimized solutionsfull-filling the “quiet zone” beam shaping must meet all 3 constraints,(6c, 6d and 6e) or (6c, 6d-1 and 6e-1) concurrently.

Concurrently, a second beam forming mechanism for a beam B_(b1) in thesecond shaped beam set implemented by a second 2-to-3 BFN 439. BP_(b1)is an input port to the beam forming network for beam B_(b1). Thetransfer function, H_B_(b1), from B_(b1) to a second set of receivingelements

$\quad\begin{bmatrix}{{Rb}\; 1} \\{{Ra}\; 1} \\{{Ra}\; 2}\end{bmatrix}$

is defined as a linear combination of [T1′], [T2′], and [T3′]; where[Ti] is the scattering matrix, a set of transfer functions, from thei^(th) transmitting element to the second set of receiving elements

$\begin{bmatrix}{{Rb}\; 1} \\{{Ra}\; 1} \\{{Ra}\; 2}\end{bmatrix}.$

$\begin{matrix}\begin{matrix}{{H\_ B}_{b\; 1} = {{{wb}\; 1*\left\lbrack {T\; 1^{\prime}} \right\rbrack} + {{wb}\; 2*\left\lbrack {T\; 2^{\prime}} \right\rbrack} + {{wb}\; 3*\left\lbrack {T\; 3^{\prime}} \right\rbrack}}} \\{= {{{wb}\; {1\begin{bmatrix}{h\; 1\; b\; 1} \\{h\; 1a\; 1} \\{h\; 1a\; 2}\end{bmatrix}}} + {{wb}\; {2\begin{bmatrix}{h\; 2\; b\; 1} \\{h\; 2a\; 1} \\{h\; 2a\; 2}\end{bmatrix}}} + {{wb}\; {3\begin{bmatrix}{h\; 3\; b\; 1} \\{h\; 3a\; 1} \\{h\; 3a\; 2}\end{bmatrix}}}}} \\{= \begin{bmatrix}{{{wb}\; 1*h\; 1\; b\; 1} + {{wb}\; 2*h\; 2\; b\; 1} + {{wb}\; 3*h\; 3\; b\; 1}} \\{{{wb}\; 1*h\; 1\; a\; 1} + {{wb}\; 2*h\; 2\; a\; 1}\; + {{wb}\; 3*h\; 3\; a\; 1}} \\{{{wb}\; 1*h\; 1\; a\; 2} + {{wb}\; 2*h\; 2\; a\; 2} + {{wb}\; 3*h\; 3\; a\; 2}}\end{bmatrix}}\end{matrix} & (7)\end{matrix}$

For OB beam shaping; beam Bb1 shall feature nulls at Rb1 and Rb2 withconstraints 1 and 2:

wb1*h1a1+wb2*h2a1+wb3*h3a1=0  (8a)

wb1*h1a2+wb2*h2a2+wb3*h3a2=0  (8b)

Beam BBb1 shall also feature a peak at Rb1 location with constraint 3:

Max(abs(wb1*h1b1+wb2*h2b1+wb3*h3b1)),  (8c)

Various optimization algorithms shall provide different solutions forthe weighting component; wa1, wa2, and wa3. Solutions full-filling theOB beam shaping for the second sets of shaped beams must meet all 3constraints, (8a, 8b, and 8c) concurrently.

For “quiet-zone” beam shaping; beam B_(b1) shall feature low intensityon flux density response on composited transfer functions at Ra1 and Ra2with constraints 4 and 5:

abs(wb1*h1a1+wb2*h2a1+wb3*h3a1)<δ1  (8d)

abs(wb1*h1a2+wb2*h2a2+wb3*h3a2)<δ1  (8e)

Beam B_(b1) shall still feature a peak at Rb1 location with constraint3:

Max(abs(wb1*h1b1+wb2*h2b1+wb3*h3b1)),  (8c)

-   -   where Max (x) is an operation to maximize x. In general, δ1        shall be less than −20 dB below the radiation level at the beam        peak; (δ1)²<(wb1*h1b1+wb2*h2b1+wb3*h3b1)2/100.

In other embodiments, there are 4 spatial-sampling points in the firstdestination; Ra1, Ra2, Ra3 and Ra4. We may define the following twoadditional components for the composited transfer function for beamB_(b1); (1) h_(bb1-a3) from the beam port BP_(b1) to Ra3, (2) h_(bb1-a4)from the beam port BP_(b1) to Ra3, the constraints 4 and 5 can bere-written as:

abs+abs(h _(bb1-a2))+abs(h _(bb1-a3))<δ1,  (8d-1)

abs(h _(bb1-a1))+abs(h _(bb1-a4))<δ1.  (8e-1)

Various optimization algorithms shall provide different solutions forthe weighting component; wb1, wb2, and wb3. Solutions full-filling the“quiet zone” beam shaping for the second sets of shaped beams must meetall 3 constraints, (8c, 8d, and 8e) or (8c, 8d-1, and 8e-1)concurrently.

As a result of preprocessing with either OB or quiet zone criteria; thetwo antennas 444 a at the first receiving sites Rx A 441 a will onlycapture radiated signal substreams; A1 and A2 delivered by beam B_(a1)and B_(a2), while the two antennas 441 b at the second receiving site RxB 441 b will only be accessible to radiated substream signals, B1 and B2delivered by beams B_(b1) and B_(b2). The received signals at Rx A areconditioned accordingly by two radios 443 a independently, and thenpost-processed by a DSP 442 a (1) to de-correlate two receivedsubstreams, A1 and A2, and (2) to de-segment the de-correlatedsubstreams for recovering received signal stream “A”.

Concurrently, the received substream signals B1 and B2 at Rx B areconditioned accordingly by two radios 443 b independently, and thenpost-processed by a DSP 442 b to recover received signal stream “B”.Thus the radiated signal streams “A” and “B” at a common RF frequencyslot are fully reconstituted at RX A and Rx B sites independently.

The “conditioning” performed by the radios 443 a and 443 b shallcomprise amplifications by low noise amplifiers (LNAs) and frequencydown conversions. However, as far as an individual user is concerned,the technique and configuration depicted on FIG. 6 is designed forfrequency re-use in a multipath dominated propagation environment butthe benefits of enhanced bandwidth for a user with multiple elementreceivers are through two shaped beams there. They are two sets of2-to-2 MIMO combined efficiently for the purposes of re-using a samefrequency and/or time slot.

In the following we shall use the constraints of orthogonal beams (OB)for “beam shaping” constraints illustrating frequency re-use functionsof multiple users in multiuser (MU) MIMO communications systems. Otherbeam-shaping constraints including “quiet-zone” constraints are equallyapplicable to techniques of MU MIMO. In highly structured and dynamicmultipath propagation environment, those techniques implemented viaquiet zone constraints over various receivers for different users mayrequire more instantaneous constraints to a user than the number ofreceiving antenna elements attached to his or her receiver. On the otherhand, those techniques implemented via OB constraints over variousreceivers for different users may require no more instantaneousconstraints to a user than the number of receiving antenna elementsattached to his or her receiver. It is the “cost” of relaying feedbackinformation in back-channels which shall dictate preference of beamshaping constraints. The information feedback “cost” includes numbers ofrequired sensors at receivers, complexity of local processing beforetransporting feedback data, and required transporting communicationsresources such as bandwidths, time slots and/or radiated powers.

FIG. 7a depicts a flow chart with a close loop optimization forcomposited transfer functions; each composited transfer function shallexhibit shaped beam features. For each frame of transmissions, MIMOcommunications systems will monitor dynamic propagation channels andgenerate or update current channel state information (CSI) by sendingprobing signals from a transmitter 401 through a communications channel405 with multiple active scattering platforms and obtaining feedbackinformation from various receivers 402. Composited transfer functions403 are formulated by summing multiple weighted transfer functionscorresponding to propagation characteristics from various transmittingelements to same sets of receiving elements on various receivers. Thepropagation characteristics usually include time delays, phase andamplitude changes for various signal frequency components and willinclude the active scattering effects from all transponding platforms.To optimize composited transfer functions using beam shaping techniques;a set of beam shaping criteria 492, such as orthogonal-beam (OB) andquiet-zone criteria, must be available to an optimization processor 493,which may be programmed to (iteratively) generate a set of optimizedweighting coefficients 494 based on algorithms; such as costminimization. Optimized composited transfer functions usually arecharacterized as shaped beams with spatially sampled constraints. Thesetransfer function constraints are measured concurrently at multiplereceiving antenna elements on various receivers.

FIG. 7b depicts a detailed formulation for the box 403 in FIG. 7a . Itis formulated based on a narrow band signal assumption. As a result, theweighting coefficients Wi comprise only time delay, phase and amplitudecomponents. It is based on current measured channel state informationCSI 4031 from various transmitting elements to different receivingelements. A component of a composited transfer function 4032, frommultiple transmit elements of a transmitter to a first receivingelement, is generated via a sum of weighted transfer function; or alinear combination of selected transfer functions. The set of theweightings shall be applied to other component of the compositedtransfer function 4032 from the same multiple transmit elements to asecond receiving element, and so on. In other words, a compositedtransfer function Bm with p selected constraints 4033 shall features pindependent spatial samples or selected components {Bm_(jk)}; or

Bm={Bm _(jk)};

where

Bm _(jk)=Σ_(i) W _(i) h _(ijk);

-   -   m the index for a shaped transmitting beam,    -   i is an index for all transmit antenna elements,    -   j and k are the indexes for the k^(th) element of a j^(th)        receiver, and    -   the summation is operated over the entire i's, or all        transmitting elements.

As a result, every shaped beam shall be constrained by p simultaneousequations 4034. To solve {W₁} 4035, we shall use these equations viaiterative optimization processing. We usually select p to be identicalto number of transmitting elements.

For wide band signal processing applications, the weighting shall beformulated, as an example, by finite impulse response (FIR) filters.There are many other wideband signal processingformulation/configurations as suggested in standard text books ondigital signal processing.

Embodiment 1

In FIG. 8, the first input data stream for a transmitter (Tx) 431,stream A, is segmented into two substream A1 and A2; followed by a firstsignal processor (SP) 4321, and then followed by a first 2-to-3 beamforming network (BFN) 439 which performs beam shaping for two concurrenttransmitting beams. The SP 4321 features 2 inputs and 2 outputs for partof space mapping functions, and the BFN 439 two inputs and threeoutputs. The first input of the BFN 439 is the for beam B_(a1) forequation (6), and the second input is for a second shaping beam fortransmitting, beam B_(a2), also featuring with a peak aimed to thesecond antenna element 444 a, Ra2 of a first user Rx A at a firstdestination and two nulls at the two elements of the antennas 444 b, Rb1and Rb2, for a second user Rx B at a second destination. The threeoutputs of the BFN 439 are connected to three radios 433 for frequencyup-conversion and power amplifications, before radiated by threetransmitting antennas 434.

The three beam shaping constraints for beam B_(a1) are equations 6a, 6band 6c for a OB beam. With the OB beam constraints, beam B_(a2) shallfeature nulls at Rb1 and Rb2 with constraints 1 and 2:

wa1*h1b1+wa2*h2b1+wa3*h3b1=0  (9a)

wa1*h1b2+wa2*h2b2+wa3*h3b2=0  (9b)

Beam B_(a2) shall also feature a peak at Ra2 location with constraint 3:

Max(abs(wa1*h1a2+wa2*h2a2+wa3*h3a2))  (9c)

With three equations of 9a, 9b and 9c (the constraints for one of the OBbeams), an optimization algorithm shall led us to an optimum set ofsolutions for wa1, wa2 and wa3 as the optimized weighting components ofa beam weighting vector (BWV) for beam B_(a2).

It is assumed that spacing between elements Ra1 and Ra2 are relativelysmall in comparison to those from Ra1 to Rb1 or Rb2, and those from Ra2to Rb1 or Rb2. Therefore, we have not imposed more stringent constraintsthan those in the example in FIG. 7a on shaped transmitting beams. Withmore performance constraints specified for a shaped transmitting beam, atransmitter would require more transmitting elements with proper elementspacing.

In a slightly modified configuration for more transmitting elements, abeam peak pointed at a first receiving element of a first user for afirst shaped OB beam shall feature a null at the second receivingelements of the first user, and two more nulls at the two receivingelements of the second user utilizing the same frequency slot. There are4 constraints for each shaped beam, and therefore at least 4 elementsare required in the transmitting array 434. The fine spatialresolutions, much finer than those derived directly for line-of-sightresolutions are results from “magnification effects” due to multipathscatting in a communication channel 150.

Referring to the configuration in FIG. 8 again, the second input datastream from the transmitter (Tx) 431, stream B, is also segmented intotwo substream B1 and B2; followed by a second signal processor (SP) 4321which, among other functions, performs a part of spatial mapping for twoconcurrent signals substreams B1 and B2. Following the SP 4321, a second2-to-3 beam forming network (BFN) 439 features 2 inputs and 3 outputs.The first input is the for beam B_(b1) for equation (8), and the secondinput is for a second shaping beam, beam B_(b2), featuring a peak aimedto Rx B 441 b but to the second antenna element Rb2 of the array 444 b,and two nulls at two elements Ra1 and Ra2 444 a for the first receiver441 a. The three outputs are connected to three radios 433, which arefollowed by three transmitting antennas 434.

Similarly, the three beam shaping constraints for beam B_(b1) areequations 8a, 8b and 8c for one of the OB beams. With the OB beamconstraints, beam B_(b2) shall feature nulls at Ra1 and Ra2 withconstraints 1 and 2:

wb1*h1a1+wb2*h2a1+wb3*h3a1=0  (10a)

wb1*h1a2+wb2*h2a2+wb3*h3a2=0  (10b)

Beam BBb2 shall also feature a peak at Rb2 location with constraint 3:

Max(abs(wb1*h1b2+wb2*h2b2+wb3*h3b2))  (10c)

With three equations of 10a, 10b and 10c, an optimization algorithmshall led us to an optimum set of solutions for wb1, wb2 and w3b3 as theoptimized weighting components of a beam weighting vector (BWV) for beamB_(b2).

The two antenna elements 444 a at the first receiving sites Rx A 441 awill only capture radiated signal substream “A1” delivered by beamB_(a1) and substream “A2” delivered by beam B_(a2), while the twoantenna elements 441 b of the second receiver Rx B 441 b at the seconddestination will only be accessible to radiated substream “B1” signalsdelivered by beam B_(b1) and the radiated substream “B2” signalsdelivered by beam B_(b2).

For the first receiver Rx A 441 a at the first destination, the receivedsignals by the first element, Ra1, of the array 444 a conditioned by afirst one of the radios 443 a, will comprise mostly information ofsubstream A1 delivered by beam B_(a1) and some leakage of substream A2radiated by beam B_(a2). Similarly, the received signals by the secondelement, Ra2, of two antennas 444 a conditioned by a second one of theradios 443 a, will comprise mostly information of substream A2 deliveredby beam B_(a2) and some leakage of substream A1 radiated by beam B_(a1).The functions of the DSP 442 a are (1) to recover received A1 and A2substreams by decoupling the correlations of the two received substreamsof signals via linear combinations, and (2) combining the recovered A1and A2 substreams to reconstitute the signal stream A.

At the site of Rx B 441 b, the received signals by the first element,Rb1, of the array 444 b conditioned by a first one of the radios 443 b,will comprise mostly information of substream B1 delivered by beam Bb1and some leakage of substream B2 radiated by beam Bb2. Similarly, thereceived signals by the second element, Rb2, of two antennas 444 bconditioned by a second one of the radios 443 b, will comprise mostlyinformation of substream B2 delivered by beam B_(b2) and some leakage ofsubstream B1 radiated by beam B_(b1). The functions of the DSP 442 b are(1) to recover received B1 and B2 substreams by decoupling correlationsof the two received substreams of signals via linear combinations, and(2) combing the recovered B1 and B2 substreams to reconstitute thesignal stream B.

At transmitting site 431 of FIG. 8, the spatial mapping functions of SP4321, and those in BFN 439 are combined in many other embodiments of MUMIMO with frequency re-use via beam shaping techniques.

Embodiment 2

In another embodiment depicted in FIG. 9, wavefrontmultiplexing/de-multiplexing (WF muxing/demuxing) are introduced fordynamic resource sharing. The only differences between FIG. 8 and FIG. 9are (1) at a transmitter (Tx) 431 m for signal stream “A” between thefirst splitter 435 and the first signal processor (SP) 4321 in FIG. 8, asuite of a wavefront multiplexing (WF muxing) processors is inserted;and (2) the current first receiver 441 am is modified by inserting asuite of wavefront demultiplexing (WF demuxing) devices between a DSP442 a and a signal combiner 445 a. We shall focus on the new additions.

At the transmitting site 431 m for a signal stream “A”, which aresegmented into A1 and A2 substreams by a first splitter 435; eachfollowed by a TDM demuxer or a serial-to-parallel (S/P) converter 438.The outputs of the demuxer or converters 438, along with pilot ordiagnostic signals (Pb) are sent to an M-to-M wavefront multiplexer 437(WF muxer) with M inputs and M outputs, where M≧3. The M outputs aregrouped into two segments; each is individually multiplexed by aconventional multiplexer 436 (such as TDM, FDM or CDM multiplexer) intoone WF muxed data stream. The two wavefront multiplexed (WF muxed) datastreams; Mux1 and Mux2, are then connected to the two inputs of thefirst SP 4321. The remaining processing for the Mux1 and Mux2 in FIG. 9,from the inputs of the first SP 4321 all the way to the three radiatingelements, are identical to those for A1 and A2 in FIG. 8. Similarly, theprocessing for data stream “B”, from the splitting/segmenting device 435all the way to the three radiating elements 434, is identical to that inFIG. 8.

There are many choices for the WF muxing transformation 437. Orthogonalmatrixes are simple because their inverse matrixes are similar to theoriginal ones. Non-orthogonal matrixes with existing inversed matrixesmay also be used for WF muxing. For many embodiments, a 256-to-256Hadamard transform is chosen as the WF muxing processor 437. The first127 input ports are for the A1 substream after converted from a fastserial flow to 127 parallel slower flows by a first TDM demuxer as thefirst serial-to-parallel converter 438. Similarly the second 127 inputports are connected to the A2 substream after converted from a fastserial flow to 127 parallel slower flows by a second TDM demuxer as thesecond serial-to-parallel converter 438. As symbolically depicted, thelast two inputs are connected to a set of probing/diagnostic signals.

The 256 outputs of the WF muxing processor 437 are 256 differentweighted sums of the 256 inputs. Each input features a uniquedistribution of its weighting parameters, a weighting vector with 256components or a wavefront with 256 components. Signals connected todifferent input ports shall exhibit various distributions of theirweighting parameters, or various weighting vectors or wavefronts. Infact, the 256 input ports to the Hadamard transform are associated with256 distinct wavefronts mutually orthogonal to one another. We will usethe orthogonal features via probing signals in receiving, to equalizepropagation channels and coherently combine received signals frommultiple paths for enhanced signal to noise ratios of received desiredsignals.

A signal stream connected to one input of the WF muxing processor 437will appear in all its outputs with a unique weighting distribution.Conversely signals from one output of the WF muxing processor 437 is aresult of a linear combination of all its input signals, which may becompletely independent and unrelated.

After WF muxed, the 256 outputs of the WF muxing process 437 are groupedinto two sets; each with 128 outputs which are multiplexed in time,frequency or coded into a single stream, Mu1 or Mu2. Mu1 and Mu2comprise information from A1, A2 and known pilot or diagnostic signalstreams, which only use less than 1%, or 2/256, of propagation bandwidthassets. By the way, the percentage of power assets for the probing ordiagnostic signals can be controlled by minimizing the input power ofthese probing signals in comparisons to these of desired communicationsdata/signal streams at the input ports from the 1^(st) to the 254^(th).

In many embodiments, pilot/diagnostic signals are connected to any inputports, not fixed for a last set of input ports of a WF muxing processor.

Referred back to the transmitter 431 m in FIG. 9, two independent datastreams A and B are segmented individually into two sets of segmentedinput data substreams (A1, A2), and (B1, B2) which are processed inparallel but through different processing. The stream A is converted tosubstreams (A1, A2), which are processed via a WF muxing transformationto become (Mu1, Mu2). They are spatially mapped by two shaped beamsformed by a first SP 4321 followed by a first 2-to-3 beam formingnetwork (BFN) 439 with 3 common outputs, which are amplified by 3 radios433 and then radiated through a set of 3 antennas 434. On the otherhand, the stream B is converted to substreams (B1, B2). They arespatially mapped by a second SP 4321 followed by a second 2-to-3 BFN 439with 3 common outputs, which are amplified by the same 3 radios 433 andthen radiated through the same set of 3 antennas 434.

As to the first receiver 441 am in a first destination, Rx A, in FIG. 9,the two antennas 444 a will only capture radiated signal WF muxedsubstream “Mu1” delivered by beam B_(a1) and WF muxed substream “Mu2”delivered by beam B_(a2). They 441 a are at nulls of the third and thefourth shaped beams B_(b1) and B_(b2) under the OB beam constraints.Similarly, the two antennas 441 b at a second destination, receivingsite Rx B 441 b, are at nulls of the first and the second shaped beamsB_(a1) and B_(a2) under the OB beam constraints, and will only beaccessible to radiated substream “B1” signals delivered by beam B_(b1)and the radiated substream “B2” signals delivered by beam B_(b2).

At the first destination of Rx A 441 a, the received signals by thefirst element, Ra1, of a two element array 444 a conditioned by a firstone of the radios 443 a, will comprise mostly information of substreamMu1 delivered by beam B_(a1) and some leakage of substream Mu2 radiatedby beam B_(a2). Similarly, the received signals by the second element,Ra2, of the two element array 444 a conditioned by a second one of theradios 443 a, will comprise mostly information of substream Mu2delivered by beam B_(a2) and some leakage of substream Mu1 radiated bybeam B_(a1). Ideally, the functions of the DSP 442 a are to recoverreceived Mu1 and Mu2 WF muxed substreams by decoupling the correlationsof the two received signal substreams via linear combinations. Since Mu1and Mu2 are heavily correlated, conventional techniques ofde-correlating Mu1 and Mu2 will not work efficiently as parts of spatialde-mapping by the SP 442 a. However, that function is carried out aspart of equalization process by a bank of the FIR filters 447 before theWF demuxing processor 448. Since we use both (1) differences 461 betweensignals from received probing signal channel and known probing signals,and (2) correlations of signals between pilot signal ports and desiredsignal ports as “cost functions” in optimization 460, the FIR filterswith optimized weighting shall realign WF muxed components of A1 and A2substreams. All cost functions shall be positive defined, and a“current” total cost is the sum of all “current” cost functions. At anoptimized state, the total cost shall be minimized. The combining device445 a will de-segment the recovered A1 and A2 substreams to reconstitutethe signal stream A.

The receiving hardware 443 a in the first destination Rx A of FIG. 9shall be identical to that in FIG. 8, but signal processing has beenreconfigured to include mainly a WF demuxing block 448 as a part ofsoftware based processing. On the other hand, the receiving processing443 b in the second destination Rx B of FIG. 9 shall be identical tothat in FIG. 8.

FIG. 10 depicts an identical configuration as that in FIG. 9, exceptmultiple bent-pipe transponder payloads 120T on a UAV 120 are shown. Thedepicted 4 transponders are independent and identical; receiving inf_(u) and transmitting in f_(d) frequency band with a finite bandwidthBW. Frequency translations are accomplished via a band of frequencyconverters. Associated low noise amplifiers (LNA) in front of theconverters and power amplifiers after the converters are depicted butnot identified. Each of the 4 transponder may feature a less than 100 Wradiated power at f_(d); such as radiation of 10 W at 1800 MHz. Thereceiving of a transponder in a forward link may feature a large fieldof view (FOV) by a single feed indicated as a triangle with a “R” symbolinside, while the transmitting in the forward link are over a smallerFOV by an array with three feeds indicated as a cluster of threetriangles with a “T” symbol inside each. The return link configuration(not shown) may be reversed. Furthermore the receiving and thetransmitting FOV's are centered at different directions. Theseindependent transponders 120T may be clustered together in a small UAV120 or distributed 10's of wavelengths away from one another in a largeUAV 120. As the UAVs move, the resulting scattering effects will bedynamically altered accordingly. The dynamic scattering from atransponder are due to varying incident and exit angles as far as aforward link data stream from a fixed ground source to various grounddestinations is concerned.

FIG. 11 depicts another forward link configuration similar to those inFIG. 9 and FIG. 10. There are two differences; (1) the ground hub 410featuring additional equipment and functions than those in the source431 m in FIG. 9; (2) multiple bent-pipe transponder payloads 120T-1 onone of the UAVs 120 as shown featuring a frequency de-multiplexingcapability via a bank of frequency converters 4120T in the forward linkto allow the ground facility 410 to “address” each of the threetransmitting elements independently; delivering various signals todifferent transmitting element. The receiving element, indicated by atriangle with an “R” in it, is for receiving signals from a feeder linkoriginated from a ground facility 410 in a background region, while thetransmitting elements, each indicated by a triangle with a “T” in it,are for radiating individually selected transponding signalsconcurrently to destinations in a foreground region 130.

The ground hub 410 features (1) high gain tracking beams generated byhigh gain tracking antennas 411 or equivalents, (2) ground based beamforming (GBBF) capability 412, and (3) mobile hub functions 413. Each ofthe high gain beams 411 tracks and communicates with at least one ofUAVs 120 individually and continuously. The GBBF 412 provides capabilityvia multiplexed wideband signals in feeder links to deliver varioustransmitting signal streams to individual transmitting elements on anyone of the UAVs 120 as indicated for the forward links communications.For return link communications via UAVs (not shown), it will be able torecover various received signals from individual receiving elements onany one of the UAVs 120 and perform further processing such as beamforming functions. The mobile hub functions 413 include all those of thesource equipment 431 m in FIG. 9 and interface or gateway functions withother terrestrial communications networks.

The depicted forward link communications payload features 4 sets ofindependent bent pipe transponders 120T-1; each with one receivingelement to capture multiplexed wideband signals comprising 3 independentsignal streams. The captured wideband signals are amplified and properlyfilter, and then sent to a 1-to-3 de-multiplexer 4120T to separate themultiplexed wideband signals into 3 individual signal streams, which arefurther amplified by individual power amplifiers before radiated bythree transmitting elements to foreground coverage 130. This payloadsupports three independent but controllable propagation paths. Thecontrols on ground by processing in the GBBF 412 for the threeindependent paths comprise modifications of propagation delays, as wellas alterations of differential amplitudes and phases.

Embodiment 3

FIG. 12 depicts a third embodiment. A point to multiple-pointcommunications system features a transmitter 431 with n transmitting(Tx) elements 434, T1, T2, T3, . . . , and Tn, where n≧4; sending twoindependent signal streams, A and B, through a multiple path dominatedchannel 150. There are 4 transmitting (Tx) beams formed by a multibeamdigital beamforming (DBF) 439 network or equivalents focused to 4different scattering regions 1501 1502, 1503, 1504 of the multipathdominated channel 150. Each of the scattering regions 1501, 1502, 1503,and 1504 comprises of multiple UAVs 120. As a result, an allocatedspectrum has been used at least four times (4×) through a multipathdominated communications via the four independent beams; b1, b2, b3, andb4. These 4 beams, featuring spot beams, shaped beams, or combinationsof spot and shaped beams, are divided into two groups; two of the 4 Txbeams as a first set of Tx beams, optimized and assigned to deliversignal stream A to a first receiver 441 a, Rx A, only. The input portsof these two beams are indicated as “b1” and “b2”. The allocatedspectrum will be utilize two times, or 2×, for the two beams. Theremaining two Tx beams, a second set of Tx beams, are optimized andassigned to service only a second receiver 441 b, Rx B. The input portsof these two beams are indicated as “b3” and “b4”, utilizing the sameallocated spectrum two more times.

There are feedback networks (not shown) for dynamic updating the channelstate information (CSI).

At the transmitter (Tx) 431, a first signal stream, stream A, to betransmitted for the first receiver 441 a, Rx A, is divided into twosegments, substreams A1 and A2, by a first splitters 438, while a secondstream, stream B, to be transmitted for the second receiver 441 b, Rx B,is divided into two segments, substreams Bland B2 by a second splitters438. Substreams A1 and A2 are pre-processed by a signal processor (SP)4321, which may include additional coding, space-time processing and/orother formatting prior to a transmitting DBF network 439; which features4 inputs and n outputs; where n≧4. The transmitting radios 433 comprisefrequency up-converters, and power amplifiers. Each may also comprisepart of modulation functions.

The depicted transmitting system, an optimized combination of thetransmitter (Tx) 431 and the transmitting array 434, supports tworeceivers, Rx A 441 a and Rx B 441 b, each with two receiving beamsusing at least two Rx elements 444 a and 444 b. The two elements, Ra1and Ra2, of the array 444 a for the first receiver 441 a, Rx A, areelectronically configured by a first 2-to-2 receiving digital beamforming (DBF) processor 449 a to efficiently capture radiated signals bythe first set of Tx beams. The two outputs of the first DBF processor449 a are indicated by b1′ and b2′ beams. Similarly, the two elements444 b, Rb1 and Rb2. for the second receiver 441 b, Rx B, are configuredby a second 2-to-2 receiving DBF processor 449 b to optimally captureradiated signals sent by the second set of Tx beams. The two outputs ofthe second DBF processor 449 b are indicated by b3′ and b4′ beams.

In a multipath dominated channel 150, there are multiple scatteringregions, st1 1501, st2 1502, st3 1503, st4 1504 for EM waves originatedfrom a transmitter to different receiver elements 444 a and 444 b. Thereis at least one of the UAVs 120 in each scattering region as activescattering platforms.

Via controlling or shaping of radiations of multiple antenna elements intransmitting side, spatial separations or isolations are achieved indelivering “A” stream and “B” stream through a multi-path dominantactive scattering to service two different users at slightly differentdestinations in a common time/frequency slot. The transmitting system,an optimized combination of the transmitter 431 and the array antenna434, delivers the first stream of data, the “A” stream,” to a firstreceiver Rx A with adequate isolations from the transmission of signalstream B.

At the first receiver Rx A 441 a, with two receiving beams formedconcurrently by the first receiving DBF 449 a from multiple receivingarray elements 444 a (at least two); Ra1 and Ra2. Substream A1 is“captured” and delivered only to a first beam port b1′ of the receivingDBF 449 a and substream A2 only to a 2nd beam port b2′ of the DBF 449 a.The radios 443 a will condition the incoming received signals. The“conditioning” includes amplifying by low noise amplifiers, bandpassfiltering, and frequency down conversions by other electronicsaccordingly. The DSP 442 a performs “de-correlation” functions betweenb1′ and b2′ substreams by a signal processor (SP) 4421 a and combiningby a de-segmenting device 448 a in which the de-correlated twosubstreams are properly combined into a reconstituted signal stream “A”.

Similarly, the transmitting system, an optimized combination of thetransmitter 431 and the transmitting antenna elements 434 willconcurrently deliver signals to the second receiver Rb, with tworeceiving beams concurrently formed by multiple array elements (at leasttwo); Rb1 and Rb2. Data substream B1 appears only to a first beam portb3′ and data substream B2 only to a 2nd beam port b4′ of the 2ndreceiver Rx B. The DSP 442 b performs both de-correlation and combiningfunctions. Spatial de-mapping functions are carried out by combinationsof the DBF 449 b and the DSP 442 b.

FIG. 13 is a special case of FIG. 12. The transmitter and the tworeceivers are identical to those in FIG. 12. The differences are in thepropagation channel 150. Multi-paths are due to scatterings of two UAVs120-1 and 120-2. There are 4 separated transmitting beams, b1, b2, b3,and b4, by the transmitter 431. A first set of two transmitting beams[b1, b2] is for receiver A 441 a, Rx A, and a second set of the othertwo beams [b3, b4] is for receiver B 441 b, Rx B. The two transmittingbeams in the first set to Rx A 441 a feature a first beam with aline-of-sight propagation and a second beam with an active scattering bya first UAV 120-1. Similarly, the two transmitting beams in the secondset to Rx B 441 b feature a third beam with line-of-sight propagationand a fourth beam with active scattering in propagation by a second UAV120-2. There are feedback networks (not shown) for dynamic updating thechannel state information (CSI).

FIG. 14 features a modified configuration to that depicted in FIG. 12.The depicted MU-MIMO configuration exhibits four time (or 4×) reuse ofan assigned spectrum for two users. Wavefront (WF)multiplexing/demultiplexing (muxing/demuxing) is incorporated fordynamic resource allocations among two users, Rx A, and Rx B. Thepropagation channel 150 is simplified. Multi-paths are due toscatterings of four UAVs 120. A digital beam forming (DBF) network 439is configured to form 4 separated transmitting beams, [b1, b2, b3, b4],in a transmitter 531 on ground for tracking 4 individual UAVs 120independently. A first set of two transmitting beams [b1, b2] is todeliver data to receiver A, Rx A 441 a, and a second set of the othertwo beams [b3, b4] is for delivering data to receiver B, Rx B 441 b. Inthe first set, a first beam continuously tracks a first UAV 120-1 and asecond beam aiming for active scattering by a second UAV 120-2.Similarly in the second set, a third beam tracks continuously a thirdUAV 120-3 and a fourth beam aiming for a fourth UAV 120-4. Eachtransmitting beam tracks and communicates with a corresponding one ofthe UAVs 120 roving over a foreground service area 130, such as an area130 in FIG. 11. There are feedback networks (not shown) for dynamicupdating the channel state information (CSI).

Referred back to the transmitter 531 in FIG. 14, two independent datastreams A and B are segmented individually into two sets of segmentedinput data substreams which are converted by programmable TDM demuxers438 and then processed in parallel along with additionalprobing/diagnostic substreams concurrently by a M-to-M WF muxingtransformation 437. The signal streams A and B after converted tosubstreams occupy, respectively, a first group and a second group ofinputs, while probing and diagnostic codes are assigned to the remaininginput ports of the M-to-M WF muxing transform 439. The M outputs aregrouped via 4 conventional multiplexers 435, e.g. 4 TDM muxers, followedby a 4-to-n digital-beam-forming (DBF) network 439 which is connected ton radiating elements 434 through a bank of n transmitting radios 433.

The 4 grouped outputs from the WF muxing transform 437 are 4 sets of WFmuxed signals, and designated as Mu1, Mu2, Mu3, and Mu4. Mu1 is sent tothe first beam port, b1, of the 4-to-n DBF network 439, dynamicallyaiming to the first UAV 120-1 and forming nulls toward the other threeUAVs 120-2, 120-3, and 120-4. The first beam is dynamic controlled via afirst beam weight vector (BWV), a set of n components using complexnumbers to dictate the signal amplitude and phase setting through the ntransmitting elements. The shaped radiation pattern and associatedwavefront are dynamically optimized. Similarly the remaining three beamsare dynamic controlled via 3 separated beam weight vectors (BWVs),aiming to the corresponding ones of the UAVs 120 and concurrentlyforming nulls toward the other three of the UAVs. These fourtransmitting beams are a set of orthogonal beams, or OB beams, withfollowing features:

-   -   A peak of a selected beam is always at nulls of other OB beams.    -   Peaks of other OB beams are always at nulls of the selected        beam.

As to the depicted first receiver 541 a in a first destination, Rx A, atleast 4 antenna elements 444 a will only capture radiated signal WFmuxed substream “Mu1” delivered by beam b1 via the first UAV 120-1,while WF muxed substream “Mu2” delivered by beam b2 via the second UAV120-2. So are the other two WF muxed substreams “Mu3” and “Mux4”delivered by beam b3 and b4 via the third and the fourth UAVs 120-3 and120-4, respectively.

A 4-to-4 receiving DBF processor 449 shall form 4 independent beams, b1′b2′ b3′ and b4′ dynamically aiming for individual UAVs 120. Eachreceiving beam may take advantage of at least 4 receiving elements toform a set of 4 OB beams. The four receiving elements are to accommodateat least 4 performance constraints for each of the 4 OB beams; oneconstraint for a specified beam peak and the remaining three fordirections of three nulls which are the beam peaks of the other three OBbeams respectively. As a result, the b1′ port shall feature recovered WFmuxed substream “Mux1,” and the b2′, b3′, and b4′ ports for therecovered WF muxed substreams “Mux2,” “Mux4,” and “Mux4,” respectively.

The 4 recovered WF muxed substreams are set to 4 demultiplexers 446,which converted them into M parallel channels before connected to a bankof adaptive equalizer 447 a, followed by a M-to-M WF demuxing transform448 a, which is programmed to output only a first group of the M outputsand additional outputs of recovered probing signals/diagnostic codes. Weuse both (1) differences 461 between signals from received probingsignal channel and known probing signals, and (2) correlations ofsignals between pilot signal ports and desired signal ports as “costfunctions” in optimization 460, the FIR filters with optimized weightingshall equalize differentials on amplitude and phase as well as timedelays among the multiple paths via various UAVs 120.

All cost functions shall be positive defined, and a “current” total costis the sum of all “current” cost functions. At a non-optimized state inan optimization 460, groups of propagation paths are not equalized.There are significant leakages among the received substreams. As aresult, there shall be strong cross-correlations among the recoveredprobing signals and recovered desired signals and significantdifferences on received probing signals with respect to a set of knownreferenced probing signals. Therefore, the total cost shall be “high”.On the other hand at an optimized state for the optimization 460, thegroups of propagation paths are equalized. There are no leakages amongthe received substreams. As a result, the total cost shall be minimized.

The combining device 445 a will de-segment all recovered substreams toreconstitute the signal stream A.

Similarly, the receiver Rx B in a second destination is identical to theone Rx A in the first destination, except the WF demuxing transform 448b or the WF demuxer is programmed to output only a second group of the Moutputs and additional outputs of recovered probing signals/diagnosticcodes. As a result, only stream B will be recovered and reconstituted atthe second destination.

It is noticed that (1) signal streams A and B are segmented andreformatted into two groups of parallel substreams (2) every substreamis sent through all 4 UAVs 120 via the M-to-M WF muxer 437 and the4-to-n DBF network 439 and (3) each of the 4 Mux is a linear combinationof all substreams from signal streams A and B. The communicationsresources comprise the available bandwidth and radiated powers supportedby the 4 UAVs 120. These radiated powers by the four UAVs 120 can beallocated to stream A or B dynamically through the input intensities ofA and B streams at the inputs of the WF muxer 437, while the totalchannel bandwidth through the communications channel 150 can beallocated to stream A or B dynamically through the controlling of numberof input ports of the WF muxer 437.

Embodiment 4

FIG. 15 depicts another MU MIMO configuration with wavefrontmultiplexing/de-multiplexing (WF muxing/demuxing) for efficient dynamicresource allocations. To highlight the key architecture features, wehave omitted implementation circuits of the updating measured CSI infeedback networks and simplified WF muxing/demuxing circuits withoptimization loops in receivers for path calibrations and equalizations.Furthermore probing/diagnostic signal injection to the WFmuxing/demuxing and Input/Output (I/O) port mapping have been discussedextensively in FIG. 14.

The transmitter 631 features 3 input data streams A1, A2, and B (or sa1,sa2, and sb), as well as two WF muxing processors 437. The configurationenables data transporting from a transmitter to three users via anallocated spectrum used four times concurrently. The first and secondusers need bandwidth allocations to accommodate their dynamic bandwidthrequirements. The third user for receiving a third data stream, B or sb,requires about twice the average bandwidth as those of sa1 and sa2 intransmissions but with a near constant bandwidth. As a result, anallocated spectrum will be used twice for transporting the sb; andanother two folds for transporting sa1 and sa2 concurrently.

In the transmitter, signals for the first two users, Rx A1 and Rx A2 aredesignated as A1 (or sa1) and A2 (or sa2). They are WF muxed via a firstWF muxing device 437, same as the one in FIG. 14, and two aggregatedoutputs of the WF muxing device 437 are sent to first two inputs of amultiple beam DBF network 439. The depicted DBF is a 4-to-n DBF; where nis the number of elements in the transmitting array 434. Concurrently,the sb for the third user Rx B is segmented into two substreams sb1 andsb2 by a divider 435 and mapped spatially by a signal process 4321; andthen WF muxed by a second WF muxing device 437 before sent to the lasttwo inputs of the 4-to-n DBF network 439. There are n correspondingtransmitting elements 434 following N radios 433, each of which performsa frequency up conversion and RF power amplification functions.

As depicted, the 4 beams shall target 4 different regions; st1 1501, st21502, st3 1503, and st4 1504. Furthermore, feedback networks (not shown)updating CSI will be used to optimize the BWVs for the four shapedtransmit beams in some embodiments. The concepts of OB beams and quietzones as shaping criteria may be implemented in the DBF networks as goodoptions in simplifying the configuration; such as replacing the spatialmapping functions by the SP 432 and thus eliminating the need for the SP4321. Two of the 4 targeted scattering regions, st1 1501 and st2 1502,are for the first receiver Rx A1 441 a and the second receiver Rx A2 441a. The remaining two; st3 1503 and st4 1504, are for the third user Rx B441 b. The three receivers depicted as Rx A1 441 a, Rx A2 441 a, and RxB 441 b respectively shall feature same hardware but programmable viasoftware control to various functional configurations as indicated. Thefirst receiver Rx A1 441 a shall have at least two receiving elements444 a; each followed by a receiving radio 443 a before a digital beamforming (DBF) network 449 a. The DBF 449 a features two output ports,connected to inputs of a WF de-muxing processor 448 a after a bank ofequalizers 447 a compensating for dynamic differentials on time delays,phases and amplitudes among propagations in various scattering regions1501 and 1502 of a multi-path dominated channel 150 dynamically.Associated optimization loops for the two receivers are not shown. Theyshall be identical to the one shown in FIG. 9. Furthermore for the firstand the second receivers, Rx A1 and Rx A2 respectively, the recoveredsignals of sa1′ and sa2′ are the output of the first and the secondoutputs of a WF demuxer 448 a. However, there are two separated WFdemuxers 448 a belonging to two spatially separated receivers, but theyare configured identically except assigned output ports.

The third receiver, Rx B, 441 b shall have at least two receivingelements 444 b; each followed by a receiving radio 443 b, before areceiving digital beam forming (DBF) network 449 b with two outputports. The radios 443 b will condition captured or received signals byassociated elements. The DBF network 449 b is connected to inputs of aWF de-muxing processor 448 b after a bank of equalizers 447 b whichdynamically compensating for differentials on time delays, phases andamplitudes among various scattering regions st3 1503 and st4 1504 ofpropagations in a multi-path dominated channel 150. The two outputs ofan associated WF demuxing device 448 b are sent to a digital signalprocessor (DSP) 442 b for further spatial de-mapping 4421 b andde-segmenting 445 b of the two recovered substreams sb1′ and sb2′ inreconstituting the recovered stream B, or sb.

FIG. 16 depicts another multi-user MIMO configuration with wavefrontmultiplexing/de-multiplexing (WF muxing/demuxing) for efficient dynamicresource allocations. It features minor modifications from FIG. 15 tosupport two users. To highlight key different features, we will notfocus on implementation circuits of updating measured CSI in feedbacknetworks and WF muxing/demuxing circuits with optimization loops inreceivers for path calibrations and equalizations. Furthermoreprobing/diagnostic signal injection to the WF muxing/demuxing andInput/Output (I/O) port mapping have been discussed extensively in FIG.14.

The transmitter (Tx) 631 a features 2 input data streams, A (or sa) andB (or sb), as well as two WF muxing processors 437. The configurationenables data transporting from a transmitter to two users via anallocated spectrum used four times concurrently. The first user needs anear constant bandwidth for receiving a first signal stream, sa, in afirst destination; and the second user in a second destination forreceiving a second signal stream sb requires about the same bandwidth asthat for the first user. Both need requirements on dynamic allocationsof received signals strength. sb in transmissions but with a nearconstant bandwidth. As a result, an allocated spectrum will be usedtwice for transporting the sb; and another two folds for transporting saconcurrently.

A first signal stream for the first user, Rx A is designated as streamA, or sa, which is segmented to two substreams; sa1 and sa2, by a firstDSP 432. The sa1 and sa2 substreams are WF muxed via a first WF muxingdevice 437, same as the one in FIG. 14, and two aggregated outputs ofthe WF muxing device 437 are sent to first two inputs of a multiple beamDBF network 439 with 4 inputs and n outputs. Concurrently, the sb forthe second user Rx B is segmented into two substreams sb1 and sb2 by asecond DSP 432. The two substreams sb1 and sb2 are then WF muxed by asecond WF muxing device 437 before sent to the last two inputs of the4-to-n DBF network 439. There are n corresponding transmitting elements434 following n radios 433, each of which performs a frequency upconversion and RF power amplification functions.

As depicted, the 4 beams shall target 4 different regions; st1 1501, st21502, st3 1503, and st4 1504. Furthermore, feedback networks (not shown)updating CSI are used to optimize beam weight vectors (BWVs) dynamicallyfor the four shaped transmit beams in some embodiments. The concepts ofOB beams and quiet zones as shaping criteria may be implemented in theDBF networks as options in simplifying the configuration; such asreplacing the spatial mapping functions in the DSP 432. Two of the 4targeted scattering regions, st1 1501 and st2 1502, are for the firstreceiver Rx A 441 a. The remaining two; st3 1503 and st4 1504, are forthe second user Rx B 441 b. The two receivers depicted as Rx A and Rx Brespectively shall feature same hardware but software programmed tovarious configurations as indicated. They shall have at least tworeceiving elements 444 a or 444 b; each followed by a receiving radio443 a or 443 b before a m_(re)-to-2 digital beam forming (DBF) network449 a or 449 b, where m_(re)≧2. The two receivers may not have the samenumbers of array elements.

A first m_(re)-to-2 DBF 449 a features two output ports, connected toinputs of a WF de-muxing processor 448 a following a bank of adaptiveequalizers 447 a compensating for differentials on time delays, phasesand amplitudes among propagations in various scattering regions 1501 and1502 of a multi-path dominated channel dynamically. Associatedoptimization loops for the two receivers are not shown. They shall beidentical to the one shown in FIG. 14. Furthermore for the firstreceiver, Rx A, the recovered signal substreams of sa1′ and sa2′ are theoutput of the first and the second outputs of a WF demuxer 448 a.

The second receiver, Rx B, 441 b shall have at least two receivingelements 444 b; each followed by a receiving radio 443 b, before asecond receiving digital beam forming (DBF) network 449 b with twooutput ports. The radios 443 b will condition captured or receivedsignals by associated elements. The second DBF network 449 b isconnected to inputs of a WF de-muxing processor 448 b after a bank ofequalizers 447 b which dynamically compensating for differentials ontime delays, phases and amplitudes among various scattering regions st34503 and st4 4504 of propagations in a multi-path dominated. The twooutputs of an associated WF demuxing device 448 b are sent to a digitalsignal processor (DSP) 442 b for further spatial de-mapping 4421 b andde-segmenting 445 b of the two recovered substreams sb1′ and sb2′ inreconstituting the recovered stream B, or sb.

Embodiment 5

FIG. 17 depicts another multi-user MIMO configuration with wavefrontmultiplexing/de-multiplexing (WF muxing/demuxing) for efficient dynamicresource allocations. To highlight the different features, we do notshow circuits for updating measured CSI in feedback networks. Thetransmitter 731 features 2 input data streams, A stream (sa) and Bstream (sb), as well as one 8-to-8 WF muxing processors 737. Theconfiguration enables data transporting from a transmitter to two usersvia an allocated spectrum used four times concurrently. Both users needdynamic allocations to accommodate their bandwidth and radiated power orEIRP requirements. The dynamic allocations are under constraints ofconstant resources on total bandwidth and on total radiated power. As aresult, an allocated spectrum will be used four times for transportingboth the sa and sb concurrently. The depicted configuration is similarto that in FIG. 14; except that there are more than one scattering UAVs120 in each of 4 scattering regions; st1 4501, st2 4502, st3 4503, andst4 4504. As a result, programming of space-time coding is implementedin both a transmitting source and receiving destinations to dynamic“accommodate” equalizing mechanisms for phase and time delaydifferentials among multiple active scattering platforms over each ofthe 4 scattering regions; st1 1501 to st4 1504. At the transmittingsource 731, DSPs 732 and a 4-to-n DBF network 439 may be used forspace-time coding. Similarly the mr-to-4 DBF 749 and DSPs 742 in adestination may also be used to accommodate space-time coding, as in aconvention p-to-p MIMO.

As depicted, signals for the two users, Rx A and Rx B, designated as saand sb are dynamically segmented into total 7 segments via two DSP 732;4 for sa and 3 for sb at one instance. They distribution may become 6for sa and 1 for sb at a second instance, or 0 for sa and 7 for sb at athird instance; and so on. The 7 substreams are sent to 7 of the 8inputs of the 8-to-8 WF muxing processor 737. The remaining inputs maybe used for probing or diagnostic signals, denoted as Pb. As depicted,the first 4 input ports are for stream A (sa), the second 3 input portsfor stream B (sb), and the last input port for Pb. The 8 outputs aregrouped into 4 groups via a bank of 4 multiplexers 736; each group isconnected to an input of a 4-beam DBF 439 which features n outputs;followed by a bank of radios 433 for signals frequency up-conversion andpower amplification before individually radiated by n transmittingelements 434. There shall be 4 shaped beams generated concurrently bythe 4-to-n DBF 439; each may be dynamically and individually optimizedvia updating an associated Beam-Weight-Vector (BWV) in some embodimentsbased on updated CSI by feedback networks (not shown). In otherembodiments the associated BWV are periodically or occasionally updatedwhen multipath dominated communications channels are nearly stationary.It is clear that there are other arrangements for the input signals viathe same WF muxing transform. In facts there exists 8! or 40,320different input arrangements for any 8-to-8 WF muxing transformationsuch as the one 737 shown in here. The high number of possible inputarrangements may be taken advantages of as part of transmission privacy.

Signals from any one of the 8 output ports of the WF muxing transform737 are results of a unique linear combination of all 8 input signalsconnected to the 8 input ports. The linear combination is a weighted sumof all 8 input signals which are completely independent. Furthermore,signals connected to any one of the 8 input ports will appear in everyone of the 8 outputs, as parts of aggregated signals. Consequently, eachof the 8 inputs of the WF muxing processor 736 is associated to adistribution of 8 weighting parameters among the 8 aggregated signals(or 8 linear combinations). The distribution of 8 weighting parametersis also referred as a wavefront vector (WFV) with a dimension of 8; orsimply as a wavefront (WF). There shall be 8 WF vectors associated withthe WF muxing transform 737. These WF vectors will be mutuallyorthogonal only when the 8-to-8 WF muxing transform 737 is implementedby an orthogonal matrix such as an 8-to-8 FFT, an 8-to-8 Hadamardmatrix, a 2×4-to-2×4 Hadamard Matrix, Cascaded FFT and Hadamardmatrixes; and etc.

As depicted, the 4 beams shall target 4 different regions; st1 1501, st21502, st3 1503, and st4 1504. Furthermore, feedback networks (not shown)updating CSI will be used to optimize BWVs for the four shaped transmitbeams. The concepts of OB beams and quiet zones as shaping criteria maybe implemented in the 4-to-n DBF networks 439. All 4 targeted scatteringregions, st1 1501, st2 1502, st3 1503 and st4 1504, are for both userswith receivers Rx A 741 a and Rx B 741 b, respectively; which shallfeature same hardware but software programmed to various functionalconfigurations as indicated.

The receiving array for a first user shall have at least four receivingelements 744 a; followed by receiving radios 443 a before a 4 beamdigital beam forming (DBF) network 749 a. The 4 beam DBF 749 a featuresfour output ports, connected to inputs of a 8-to-8 WF de-muxingprocessor 448 a after a bank of demultiplexers 746 a and adaptiveequalizers 447 a which dynamically compensating for differentials ontime delays, phases and amplitudes among propagations in variousscattering regions 1501 to 1504 of a multi-path dominated channel 150.The first 4 of the 8 outputs from the WF demuxing processor 448 a areallocated for the first signal stream sa for the first receiver, Rx A741 a. One output of the WF demuxer 448 a is assigned to recoveredprobing signals Pb′ which will be compared to a known probing signal Pb.The differences 461 are indexed as cost functions for an optimizationprocessor 460 to calculate weighting parameters for the bank ofequalizers 447 a. The detailed processing shall be identical to the oneshown in FIG. 14. Before reaching an optimized state of the equalizers,the assigned 4 outputs of the WF demuxer 448 a shall feature significantcross-coupling of Pb to the 4 output ports for recovering substreamssa1′, sa2′, sa3′, and sa4′. There shall be major difference betweenrecovered signals from the recovered Pb port and the known a priori Pbsignals. Various positively defined cost functions are formed base onthese measurements. Current total cost is a sum of all cost functionsfrom updated measurements. Optimization 460 is carried out to findupdated coefficients or parameters for the adaptive equalizers via acost minimization algorithm based on measured current total cost andderived gradients on total cost.

At an optimized state of the equalizers 447 a, the assigned first 4outputs of the WF demuxer 448 a will recover the 4 substreams sa1′,sa2′, sa3′, and sa4′. The de-segmenting unit 742 a will perform spatialde-mapping further before combining all 4 substreams; sa1′ sa2′, sa3′,and sa4′, into a reconstituted stream A or sa′.

Furthermore a second receiver, Rx B 741 b features identical functionsas those in the first receiver, Rx A 741 a. It shall have at least fourreceiving elements 744 b; each followed by a receiving radio 443 b,before a receiving digital beam forming (DBF) network 449 b with twooutput ports. The WF demuxers 448 b is configured identically to the one448 a except assigned output ports. The three outputs of an associatedWF demuxing device 448 b are sent to a digital signal processor (DSP)742 b for further spatial de-mapping and de-segmenting of the threerecovered substreams sb1′ sb2′ and sb3′ in reconstituting the recoveredstream B, or sb.

In other embodiments, the WF muxing device 737 may be implemented,instead of a 8-to-8 WF muxer, by a 1024-to-1024 Hadamard transform with1024 input ports and 1024 output ports. The 1024 output ports aregrouped by 4 sets of 256-to-1 TDM multiplexers into 4 streams before the4-to-n DBF 439. The 1024 input ports are shared by the two user streams(sa and sb) in forms of multiple segmented substreams in parallel viatwo DSP 732 and a set of probing or diagnostic signals. To dynamicallyallocating available bandwidth, the input port distribution for the WFmuxing device 737 among two signal streams, sa and sb, and probingstreams in forms of [sa, sb, pb] may be dynamically altered amongdistributions of [1023, 0, 1], [512, 510, 2], [128, 890, 6], [20, 1000,4], [0, 1023,1], and others.

Embodiment 6

FIG. 18 depicts another multi-user MIMO configuration with wavefrontmultiplexing/de-multiplexing (WF muxing/demuxing) for efficient dynamicresource allocations. To highlight the key architecture features, we donot show circuits for updating measured CSI in feedback networks. Thetransmitter 831 features 2 input data streams, A stream (sa) and Bstream (sb), as well as one 8-to-8 WF muxing processors 737. Theconfiguration enables data transporting from a transmitter to two usersvia an allocated spectrum used four times concurrently. The four beamsare generated by 4 high gain antennas 834 pointing to various portionsof the propagation. Both users need dynamic allocations to accommodatetheir bandwidth and radiated power or EIRP requirements. The dynamicallocations are under constraints of constant resources on totalbandwidth and on total radiated power. As a result, an allocatedspectrum will be used four times efficiently for transporting both thesa and sb concurrently.

In comparing to the configuration in FIG. 17, the propagation and thereceivers 741 a and 741 b in FIG. 18 are identical to those in FIG. 17.We will not repeat descriptions on these items again in here. We shallfocus on the differences in the transmitter 831 in FIG. 18 and the one731 in FIG. 17. The mechanisms of forming 4 shaped beams, amplifyingsignals and radiating power-amplified signals in FIG. 17 comprise of a4-to-n DBF 439 followed by n radios 433, and n antenna elements 434,each antenna element shall feature a low gain and broad beam radiationpattern. On the other hand, there are no beam forming mechanisms exceptgeometries of the 4 high gain radiators 834; A1, A2, A3, and A4. We havealso separately added a power-amplifier stage 833Am in each of the4-radios 833.

As depicted on the transmitter 831 in FIG. 18, signals for the twousers, Rx A and Rx B, designated as sa and sb are dynamically segmentedinto total 7 segments via two DSP 732; 4 for sa and 3 for sb at oneinstance. They distribution may become 6 for sa and 1 for sb at a secondinstance, or 0 for sa and 7 for sb at a third instance; and so on. The 7substreams are sent to 7 of the 8 inputs of the 8-to-8 WF muxingprocessor 737. The remaining input may be used for probing or diagnosticsignals, denoted as Pb. As depicted, the first 4 input ports are forstream A (sa), the second 3 input ports for stream B (sb), and the lastinput port for Pb. The 8 outputs are grouped into 4 groups via a bank ofmultiplexers 736; each group is connected to an input of a high gainradiator 834 after frequency up-converted by a radio 833 and amplifiedby a power amplifier 833Am. Beam shaping are implemented in the 4 highgain radiators 834 such as reflectors through techniques of digital oranalogue beam forming networks or customized reflector mechanicalsurface contours.

Embodiment 7

FIG. 19 depict another multi-user MIMO (MU-MIMO) configuration withwavefront multiplexing/de-multiplexing (WF muxing/demuxing) forefficient dynamic resource allocations. To highlight the keyarchitecture features, we do not show circuits for updating measured CSIin feedback networks. The transmitter 931 features 2 input data streams,A stream (sa) and B stream (sb), as well as one 8-to-8 WF muxingprocessors 737. The configuration enables data transporting from atransmitter to two users via an allocated spectrum used four timesconcurrently. The four beams are generated by 4 antennas 834 pointing tovarious portions of the propagation. The first two elements, A1 and A2,feature radiation patterns of low gain and wide angular coverage; andthe remaining two, A3 and A4, are high gain, spot of shaped beamantennas. Both users need dynamic allocations to accommodate theirbandwidth and radiated power or EIRP requirements. The dynamicallocations are under constraints of constant resources on totalbandwidth and on total radiated power. As a result, an allocatedspectrum will be used four times efficiently for transporting both thesa and sb concurrently.

In comparing to the configurations in FIG. 17 and FIG. 18, thepropagation channel 150 and the receivers 741 a and 741 b in FIG. 19 areidentical to those in FIG. 17 and those in FIG. 18. We will not repeatdescriptions on these items again in here. We shall focus on thetransmitter 931 in FIG. 19. The mechanisms of forming 4 shaped beams,amplifying signals and radiating power-amplified signals in FIG. 17comprise of a 4-to-n DBF 439 followed by n radios 433, and n antennaelements 434. Each antenna shall feature a low gain and broad beamradiation pattern. On the other hand, there are no beam formingmechanisms except geometries of the 4 radiators 834; 2 elements A1, andA2 featuring low gain broad beams and the other 2 antennas A3, and A4featuring high gain shaped beams. We have also separately added apower-amplifier stage 833 am following each radios 833.

Radiations from A1 and A2 cover a field-of-view (FOV) of st1 1501 and aFOV of st2 1502, respectively, flooding large access portions of thecommunications channel 150. On the other hand, radiations from A3 and A4cover FOVs of st3 1503 and a FOV of st4 1504, respectively, focusing onlimited access portions of the same communications channel 150.

As depicted on the transmitter 931 in FIG. 19, signals for the twousers, Rx A and Rx B, designated as “A stream” or sa and “B stream” orsb are dynamically segmented into total 7 substreams (or segments) viatwo DSP 732; 4 for sa and 3 for sb at one instance. They distributionmay become 6 for sa and 1 for sb at a second instance, or 0 for sa and 7for sb at a third instance; and so on. The 7 substreams are sent to 7 ofthe 8 inputs of a 8-to-8 WF muxing processor 737. The remaining inputmay be used for probing or diagnostic signals, denoted as Pb. Asdepicted, the first 4 input ports are for stream A (sa), the second 3input ports for stream B (sb), and the last input port for Pb.

The 8 outputs are grouped into 4 groups via a bank of multiplexers 736;each group is connected to an input of an antennas 834 after frequencyup-converted by a radio 833 and amplified by a power amplifier 833Am.Beam shaping are implemented only in the 2 high gain radiators 834 A3and A4 such as reflectors through techniques of beam forming networks orcustomized reflector mechanical surface contours. There is nobeam-forming for A1 and A2 antenna elements. The multiplexers 736 intransmitter 931 and the corresponding de-multiplexers 746 in receivers741 a and 741 b shall be conventional pairs for muxing/demuxing in adomain space of frequency (FDM), time (TDM), or code (CDM).

Embodiment 8

FIG. 20 depict another multi-user MIMO configuration with wavefrontmultiplexing/de-multiplexing (WF muxing/demuxing) for efficient dynamicresource allocations. To highlight the key architecture features, we donot show circuits for updating measured CSI in feedback networks. Thetransmitter 931 features 2 input data streams, A stream (sa) and Bstream (sb), which go through a common 8-to-8 WF muxing processors 737.The configuration enables data transporting from a transmitter to twousers via an allocated spectrum re-used four times concurrently. Thefour beams are generated by antennas 834 pointing to various portions ofthe propagation. Both users need dynamic allocations to accommodatetheir bandwidth and radiated power or EIRP requirements. The dynamicallocations are under constraints of constant resources on totalbandwidth and on total radiated power. As a result, an allocatedspectrum will be used four times efficiently for transporting both thesa and sb concurrently.

In comparing to the configurations in FIG. 19, the propagation channel150 and the receivers 741 a and 741 b in FIG. 20 are identical to thosein the two figures We will not repeat descriptions on these items againin here. We shall focus on the transmitter 1031 in FIG. 20.

There are two different sets of beam forming mechanisms includinggeometries of the 4 radiators 834. The 2 elements, A1 and A2, featuringlow gain broad beams are organized by a 2-to-2 transmitting DBF network439 in forming two independent beams. Depending on the spacing betweenthe elements and associated beam weight vectors, there will be twoshaped beams generated. The transmitting patterns from the other 2antenna elements; A3 and A4 shall feature high gain shaped beams. Wehave also separately added a power-amplifier stage 833 am following eachof the 4-radios 833. Beam shaping for the 2 high gain radiators 834 A3and A4 may be through techniques of beam forming networks among a feedarray near focal regions of a reflector or those with a feedilluminating a reflector with customized mechanical surface contours.

In other different embodiments, the 4 elements 834 in FIG. 20 mayfeatures 4 different element patterns; and 4 shaped beams are results ofvarious configurable linear combinations of the 4 element beams by amultibeam beam forming network or equivalents; implemented by analogueand/or digital devices/circuits.

Embodiment 9

FIG. 21 features a point-to-point (p-to-p) MIMO configuration exhibitsfour time (or 4×) reuse of an assigned spectrum, and can be extended toa point-to-multipoint (p-to-mp) version as the one in FIG. 14. Wavefront(WF) multiplexing/demultiplexing (muxing/demuxing) is incorporated tocoherent power combining for the scattered radiations from the UAVs 120;a first UAV 120-1 to a fourth UAV 120-4. The transmitter and thereceiver are modified accordingly from those in FIG. 14. Thecommunications is identical to that in FIG. 14. Multi-paths are due toscatterings of four UAVs 120.

From the ground facility 531, there are 4 separated transmitting beams,[b1, b2, b3, b4], by the transmitter 531 tracking and communicating withall four UAVs 120 individually, while they 120 are roving over aforeground service area 130. There are feedback networks (not shown) fordynamic updating the channel state information (CSI).

Referred back to the transmitter 531, a signal stream A, say at 7×10⁹samples per second or 7 Gsps as a numerical example, are segmented intoa set of 7 segmented input substreams; sa1 to sa7, which are convertedby programmable TDM demuxers 438 and then processed in parallel alongwith additional probing/diagnostic substreams (not shown) concurrentlyby a 8-to-8 WF muxing transformation 437. The signal stream A afterconverted to substreams occupy, respectively, 7 parallel inputs at a 1Giga-samples per second (1 Gsps) rate each, while probing and diagnosticcodes are assigned to the last input port of the 8-to-8 WF muxingtransform 439 also clocked at 1 Giga-samples per second. With 8 parallelchannels, the WF muxer 437 operates at a data rate of 8 Gsps. The 8outputs, each at 1 Gsps, are grouped via 4 conventional multiplexers435, e.g. 4 sets of 2-to-1TDM muxers, followed by a 4-to-ndigital-beam-forming (DBF) network which is connected to a defocused RFlens with n feed array elements 434 through a bank of n radios withpower amplifiers 433. The 4 grouped outputs from the WF muxing transform437 are 4 sets of WF muxed signals flowing in a 2 Gsps rate, anddesignated as Mu1, Mu2, Mu3, and Mu4. Mu1 is sent to the first beamport, b1, for the 4-to-n DBF network (shown in FIG. 14 only), aiming toa first UAV 120-1 dynamically and forming nulls toward the other threeUAVs 120-2, 120-3, and 120-4. The first beam is dynamic controlled via afirst beam weight vector (BWV), a set of n components using complexnumbers to dictate the signal amplitude and phase setting through the ntransmitting elements of the feed array 434. The shaped radiationpattern and associated wavefront are dynamically optimized.

Similarly the remaining three beams are dynamic controlled via 3separated beam weight vectors (BWVs), aiming to the corresponding onesof the four UAVs 120 and concurrently forming nulls toward the otherthree of the UAVs. These four transmitting beams are a set of OB beamswith following features:

-   -   A peak of a selected beam is always at nulls of other OB beams.    -   Peaks of other OB beams are always at nulls of the selected beam

As to the depicted receiver 541 a in a first destination, Rx A, areceiving antenna comprising of a reflector with a feed array 444 a anda receiving beam forming network (BFN) 449 a, will only capture radiatedsignal WF muxed substream “Mu1” delivered by beam b1 via the first UAV120-1, while WF muxed substream “Mu2” delivered by beam b2 via thesecond UAV 120-2. So are the other two WF muxed substreams “Mu3” and“Mux4” delivered by beam b3 and b4 via the third and the fourth UAVs120-3 and 120-4, respectively. The four tracking beams at thedestination will be dynamically formed by a 4 beam receiving BFN 449 a.The received signals will be amplifier and down converted by a bank ofreceiving radios (not shown), followed by a bank of adaptive equalizers447 a before a coherent power combining process in a WF demuxer 448 a.

Equalizers are iteratively optimized via a optimization process 460 todynamically compensate for phase differentials through differentscattering paths by 4 separated UAVs 120. The equalization processingand associated parameters are identical to the ones in FIG. 10. We shallnot repeat them again in here.

When the equalizers 447 a are fully optimized, the propagation pathsthrough the 4 UAVs 120 are fully equalized at the interface between theadaptive equalizers 447 a and the WF demuxer 448 a. There are noleakages among the substreams at the output ports of the WF demuxer 448.For instance the recovered probing signal substreams is the output fromthe 8^(th) port of the WF demuxer; which delivers, sample-by-sample, alinear combined result from the samples from all 8 inputs weighted by acorresponding WF vector for the probing signal. When the 8 inputs arefully compensated; the linear combination operation shall produceresults with two unique features:

-   -   Components of the desired signal distributed in the 8 inputs        after weighted by the corresponding WF vector shall be line-up        in phase,    -   Components of any one of the 7 undesired inputs distributed in        the 8 weighted inputs shall be destructively interfered to        cancel one another.

At fully equalized states, the 8 outputs from the WF demuxing transform448 a comprise two groups of signals. The first group from port 1 toport 7 features recovered signal substreams sa1′ to sa7′, which arefollowed by a 7-to-1 TDM multiplexer converting the 7 parallelsubstreams, each at 1 Gsps as in the numerical example, into areconstituted signal stream A at 7 Gbps. The second output group fromthe 8^(th) port is used by probing and diagnostic signal at a rate of 1Gsps. The probing signals occupy 12.5% of total available bandwidth.

FIG. 22 depicts a similar p-to-p configuration as that in FIG. 21,except the 4 UAVs 120-1 to 120-4 are replaced by a swarm of small ormicro UAVs 120, each radiated normally less than 5 watt RF power. TheseUAVs are slow moving platforms staying over an airspace with a volume of˜km in diameters indicated by a large circle with 8 smaller circles. TheUAV distributed volume is indicated by the large circle graphicallydimension-wise. The spacing among the UAVs are smaller than angularresolutions of both multi-element antennas 434 of a ground transmitter531 and a receiver 444 a. Resolutions of the transmitting antenna 434are indicated by the smaller circles. A first radiation signal streamoriginated from a first feed element of the transmitting antenna 434,which is a multibeam lens, will illuminate over a finite bandwidth on agroup of micro UAVs in a first one of the 8 smaller circles. The firstsmall circle shall feature N1u small UAVs, each shall have at least onetransponder with one receiving and one transmitting elements, whereN1u≧1. The collectively scattered first signal stream from the N1u smallUAVs will be re-radiated toward a foreground coverage area 130 and shallbe captured by multiple antenna elements of a desired receiver 541 a. VThe number of small UAVs within a small circle may gracefully bealerted, as the UAVs hovering in/out of their assigned airspace.Similarly a second signal stream from a second antenna element of thetransmitter 531 shall be actively scattered by N2u UAVs in a secondsmaller circle toward the desired receiver 541 a, where N2u≧1. There are8 independent signal streams initiated from the multibeam antenna 434 ofthe transmitter 531, scattered by the swarm of UAVs 120, and arriving atthe multiple elements of the receiving antenna 444 a of the receiver 541a over the same bandwidth. With proper post processing in the receiver541 a, channel capacity of the multipath communications channel 150between the transmitter 531 and the receiver 541 a remotely located hasbeen multiplied by 8 times via active scattering of the small UAVs 120.

The multiple-time channel capacity between the transmitter 531 and thereceiver 541 via swarm of UAVs are implementable even the transmitantenna 444 a becomes a multi-element array (not shown) in otherembodiments. It is also possible to extend active scatteringapplications of swarm of UAVs 120 for point-to multipoint (p-to-mp)communications with multiple times of frequency reuse. With 10 radiatingelements (not shown) in a transmitter antenna 434, it is possible toallocate 7× bandwidth for a channel capacity from the transmitter 531connecting to a first receiver 541 a, and concurrently 3× bandwidth fromthe same transmitter 531 connecting to a second receiver (not shown) inthe coverage 130, under the following assumptions;

i. There are no less than 10 mini UAV's in the swarm, and each UAVsfeaturing a single transponder with one receiving and one transmittingantenna element.

-   -   ii. The transmitter features no less than 10 radiating elements.    -   iii. The first receiver has no less than 7 elements, while the        second one with no less than 3 elements.

FIG. 23 depicts similar configuration as that in FIG. 22, except theswarm of small or micro UAVs 120, each radiated normally less than 5watt RF power is spatially separated into multiple groups.

FIG. 24 depicts similar configuration of that in FIG. 21, except the WFmuxing are applied in transmitters to streams of data before they aremodulated by a modulator 1135 to become signal streams, and WF demuxingin receivers are applied recovered signal streams after they aredemodulated to become recovered data streams by a demodulator 1145. Atransmitter 531 is programmed to enable an un-modulated input datastream, A, segmented into multiple parallel substreams by a TDM demuxer438, or an equivalent, followed by a M-to-M WF muxing transform 437. Theoutputs of the TDM demuxer 438 only occupy, say, 75% of the M inputports. For cases with M=16, 12 inputs are for connections to the TDMdemuxers. The remaining 4 are for connections to known signals fordiagnostic or redundancies. The M WF muxed data streams from the Moutputs are grouped into 4 streams via 4 multiplexing devices beforesent to a bank of modulators 1135 followed by a 4 beambeam-forming-networks (BFN) 439, transmitting radios 433 and then amultiple beam antenna 434.

As a result, modulations are on 4 grouped WF muxed data streams. The 4modulated signal streams after the modulators 1135 are frequencyup-converted and amplified before radiated toward 4 separated UAVs 120.Each UAV 120-1, 120-2, 120-3, or 120-4 carries a modulated signalsstream from one of the four grouped WF muxed data substreams.

In order to recover desired data streams Ai′ at a first destination, thereceiver 541 a shall be accessible to, at least, any three of the fourUAVs 120. A receive 541 a is programmed from the configuration in FIG.21 to an alternate configuration with a bank of demodulators 1145following a receiving beam-forming network (BFN) 449 a for 4 trackingbeams and before a bank of adaptive equalizers 447 a and a WF demuxingtransform 448 a. The demodulators shall convert received signals(waveforms) into data substreams. The optimization process 460 is toalign the timing among the data substreams normally via adaptiveequalizers 447 a.

The depicted approach is for “non-coherent” WF muxing/de-muxingapplications to enhance reliability and security of data transportthrough the active scattering communications, while those configurationsin FIGS. 21, 22,23 are for “coherent” WF muxing/de-muxing applications,to enable (1) coherent power combining and/or (2) efficient dynamiccombined resource allocations through the multipath dominatedcommunications with multiple scattering UAVs 120.

It is possible in MIMO communications architecture with multiple activescattering UAVs 120 to switch between the depicted configuration in FIG.21 and that in FIG. 24 through software reprogramming on bothtransmitting equipment at sources and receiving user equipment atdestinations. It is also possible to allow both configurations throughthe same set of UAVs 120.

FIG. 25 depicts similar configuration as that in FIG. 21, except the 4UAVs 120 are replaced by multiple satellites 1220. These satellites1220-1 to 1220-4 may be in various earth orbits with radiated 10s wattor 100s watt of RF power each.

FIG. 26 depicts similar configuration as that in FIG. 25, except thesmall or micro satellites 1220, each radiated normally less than 100swatt of RF power are spatially separated into multiple groups.

FIG. 27 depicts similar configuration as that in FIG. 25, except the WFmuxing are applied in transmitters to streams of data before they aremodulated by a modulator 1135 to become signal streams, and WF demuxingin receivers are applied recovered signal streams after they aredemodulated by a demodulator 1145 to become recovered data streams. Atransmitter 531 is programmed to enable an un-modulated input datastream, Ai, segmented into multiple parallel substreams by a TDM demuxer438, or an equivalent, followed by a M-to-M WF muxing transform 437. Theoutputs of the TDM demuxer 438 only occupy 75% of the M input ports. Forcases with M=16, 12 inputs are for connections to the TDM demuxers. Theremaining 4 are for connections to known signals for diagnostic orredundancies. The M WF muxed data streams from the M outputs are groupedinto 4 streams via 4 multiplexing devices before sent to a bank ofmodulators 1135 followed by a 4 beam beam-forming-networks (BFN) 439,transmitting radios 433 and then a multiple beam antenna 434. As aresult, modulations are on 4 grouped WF muxed data streams. The 4modulated signal streams after the modulators 1135 are frequencyup-converted and amplified before radiated toward 4 separated UAVs 120.Each UAV 120-1, 120-2, 120-3, or 120-4 carries a modulated signalsstream from one of the four grouped WF muxed data substreams.

In order to recover desired data streams A at a first destination, thereceiver 541 a shall be accessible to, at least, any three of the foursatellites 1220. A receive 541 a is programmed from the configuration inFIG. 25 to an alternate configuration with a bank of demodulators 1145following a receiving beam-forming network (BFN) 449 a for 4 trackingbeams and before a bank of adaptive equalizers 447 a and a WF demuxingtransform 448 a. The demodulators shall convert received signals(waveforms) into data substreams. The optimization process 460 is toalign the timing among the data substreams normally via adaptiveequalizers 447 a.

The depicted approach is for “non-coherent” WF muxing/de-muxingapplications to enhance reliability and security of data transportthrough the active scattering communications, while those configurationsin FIGS. 12, and 12 a are for “coherent” WF muxing/de-muxingapplications, to enable (1) coherent power combining and/or (2)efficient dynamic combined resource allocations through the multipathdominated communications with multiple transponding satellites 1220.

FIG. 28 depicts similar configuration as that in FIG. 26, except thesome spatially separated groups of the satellites 1220 are replaced byclusters of mini UAVs 120.

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What is claimed is:
 1. A communication system comprising: a transmittercomprising: a beam forming network having M input ports, for receiving Msignals destined for one or more remote receivers and transforming the Msignals into a set of shaped beams, M being an integer greater than orequal to 2; a set of transmitting radios coupled to the beam formingnetwork, for conditioning the shaped beams for transmission, theconditioning including low-noise amplifying and frequency downconverting; a set of first antenna elements coupled to the transmittingradios for radiating the conditioned shaped beams toward one or moreactive scattering platforms; the one or more active scattering platformsfor receiving one or more of the conditioned shaped beams andre-radiating the one or more of the conditioned shaped beams toward theone or more remote receivers; and the one or more remote receivers, eachof which comprising a corresponding set of second antenna elements, forreceiving the one or more of the conditioned shaped beams; wherein thebeam forming network performs optimization for the shaped beams byoptimizing composite transfer functions under performance constraints,each of the composite transfer functions being a linear combination oftransfer functions, each of the transfer functions characterizing atleast one propagation path from one of the first antenna elements of thetransmitter to one of the second antenna elements of a correspondingremote receiver of the one or more remote receivers, each of the secondantenna elements being identified by a user element identification indexin the transfer functions, each of the one or more remote receiversbeing identified by a user identification index, the performanceconstraints being specified for locations identified by the useridentification indices or the user element identification indices. 2.The communication system of claim 1, wherein each of the one or moreremote receivers further comprises: a set of receiving radios coupled tothe second antenna elements, for amplifying, bandpass filtering, andfrequency down converting the received one or more of the conditionedshaped beams.
 3. The communication system of claim 2, wherein each ofthe one or more remote receivers further comprises: a receiving beamforming network coupled to the receiving radios, for forming receivingbeams via the second antenna elements to capture the one or more of theconditioned shaped beams, and outputting corresponding received shapedbeams.
 4. The communication system of claim 2, wherein the transmitterfurther comprises: an encoder coupled to one of the M input ports of thebeam forming network, for encoding a probing signal using a spreadingcode and outputting the encoded probing signal as one of the M signals;and wherein each of the one or more remote receivers further comprises:a decoder coupled to the set of second antenna elements, for receivingand de-spreading the received one or more of the conditioned shapedbeams to generate a recovered probe signal which is a recovered versionof the probe signal.
 5. The communication system of claim 2, wherein thetransmitter further comprises: a digital signal processor coupled to thebeam forming network, for processing and segmenting an input stream intoa set of substreams, and outputting the set of substreams as a subset ofthe M signals.
 6. The communication system of claim 5, wherein each ofthe one or more remote receivers further comprises: a digital signalprocessor coupled to the receiving radios, for receiving the receivedone or more of the conditioned shaped beams that contain the set ofsubstreams, de-correlating the received substreams, and de-segmentingthe de-correlated substreams to generate a recovered input stream whichis a recovered version of the input stream.
 7. The communication systemof claim 3, wherein the transmitter further comprises: a first digitalsignal processor coupled to the beam forming network, for processing andsegmenting an input stream into a set of substreams, and outputting theset of substreams as a subset of the M signals; and wherein each of theone or more remote receivers further comprises: a second digital signalprocessor coupled to the receiving beam forming network, for receivingthe received shaped beams that contain the set of substreams,de-correlating the received substreams, and de-segmenting thede-correlated substreams to generate a recovered input stream which is arecovered version of the input stream.
 8. The communication system ofclaim 1, wherein the one or more active scattering platforms areairborne and comprise a plurality of transponders.
 9. The communicationsystem of claim 1, wherein the one or more remote receivers are on oneor more mobile platforms.
 10. The communication system of claim 1,wherein the transmitter is on an airborne platform and the one or moreactive scattering platforms are ground-based or on an ocean surface. 11.A communication system comprising: a transmitter comprising: a wavefrontmultiplexer having M input ports and M output ports, for receivingconcurrently M input signals destined for one or more remote receivers,performing an M-to-M wavefront multiplexing transform on the M inputsignals and outputting the M signals such that each of the M signals isa unique linear combination of the M input signals, the wavefrontmultiplexing transform having an inverse transform. a beam formingnetwork coupled to the wavefront multiplexer for receiving M signals andtransforming the M signals into a set of shaped beams, M being aninteger greater than or equal to 2; a set of transmitting radios coupledto the beam forming network, for conditioning the shaped beams fortransmission, the conditioning including low-noise amplifying andfrequency down converting; a set of first antenna elements coupled tothe set of transmitting radios for radiating the conditioned shapedbeams toward one or more active scattering platforms; the one or moreactive scattering platforms for receiving one or more of the conditionedshaped beams and re-radiating the one or more of the conditioned shapedbeams toward the one or more remote receivers; and the one or moreremote receivers, each of which comprising a corresponding set of secondantenna elements, for receiving the one or more of the conditionedshaped beams; wherein the beam forming network performs optimization forthe shaped beams by optimizing composite transfer functions underperformance constraints, each of the composite transfer functions beinga linear combination of transfer functions, each of the transferfunctions characterizing at least one propagation path from one of thefirst antenna elements of the transmitter to one of the second antennaelements of a corresponding remote receiver of the one or more remotereceivers, each of the second antenna elements being identified by auser element identification index in the transfer functions, each of theone or more remote receivers being identified by a user identificationindex, the performance constraints being specified for locationsidentified by the user identification indices or the user elementidentification indices.
 12. The communication system of claim 11,wherein the transmitter further comprises: a time-domain demultiplexercoupled to L input ports of the M input ports of the wavefrontmultiplexer, L being an integer smaller than M, for transforming aninput signal stream into L input signals of the M input signals.
 13. Thecommunication system of claim 11, wherein the M input signals comprise Ldata signals and M minus L diagnostic signals, L being a positiveinteger smaller than M, the M minus L diagnostic signals being known apriori to the one or more remote receivers.
 14. The communication systemof claim 11, wherein each of the one or more remote receivers furthercomprises: a set of receiving radios coupled to the second antennaelements, for amplifying, bandpass filtering, and frequency downconverting the received one or more of the conditioned shaped beams; areceiving beam forming network coupled to the receiving radios, forforming receiving beams via the second antenna elements to capture theone or more of the conditioned shaped beams, and outputting a set ofreceived shaped beams; a set of equalizers coupled to the receiving beamforming network for equalizing the received shaped beams; and awavefront demultiplexer coupled to the equalizers, for performing theinverse of the wavefront multiplexing transform on the received shapedbeams and generating a set of recovered signals, the set of recoveredsignals being a recovered version of at least a subset of the M inputsignals.
 15. The communication system of claim 14, wherein thetransmitter further comprises: a first digital signal processor coupledto the wavefront multiplexer, for processing and segmenting an inputstream into a set of substreams, and outputting the set of substreams asa first subset of the M input signals; and wherein each of the one ormore remote receivers further comprises: a second digital signalprocessor coupled to the wavefront demultiplexer, for receiving therecovered signals that contain the set of substreams, spatial de-mappingand de-segmenting the recovered substreams, and generating a recoveredinput stream which is a recovered version of the input stream.
 16. Thecommunication system of claim 13, wherein each of the one or more remotereceivers further comprises: a set of receiving radios coupled to thesecond antenna elements, for amplifying, bandpass filtering, andfrequency down converting the received one or more of the conditionedshaped beams; a receiving beam forming network coupled to the receivingradios, for forming receiving beams via the second antenna elements tocapture the one or more of the conditioned shaped beams, and outputtinga set of received shaped beams; a set of equalizers coupled to thereceiving beam forming network for equalizing the received shaped beams;a wavefront demultiplexer coupled to the equalizers, for performing theinverse of the wavefront multiplexing transform on the received shapedbeams and generating a set of output signals, the set of output signalsbeing a recovered version of at least a subset of the M input signalsand including recovered diagnostic signals; and an optimizationprocessor coupled to the wavefront demultiplexer and the equalizers, forcalculating updated values of weighting parameters for the equalizerssuch that a total cost function is minimized, the total cost functionincluding at least a function of differences between the recovereddiagnostic signals and the known a priori diagnostic signals.
 17. Thecommunication system of claim 11, wherein the one or more activescattering platforms are airborne and comprise a plurality oftransponders.
 18. The communication system of claim 11, wherein thetransmitter is on a mobile platform.
 19. The communication system ofclaim 11, wherein the one or more remote receivers are on one or moremobile platforms.
 20. The communication system of claim 11, wherein thetransmitter is on an airborne platform and the one or more activescattering platforms are ground-based or on an ocean surface.